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The Aggressive Response Meter (ARM) has been validated for measuring emotional (psychotic) aggression triggered by mental irritation in mice. In the present article, we newly developed a device, pARM (PowerLab-compatible type ARM). We collected on the aggressive biting behavior (ABB) intensity and ABB frequency of 20 male and female mice of ddY strain studied over a period of 6 days by using pARM and the former ARM. We calculated Pearson's correlation between the values of pARM and those of ARM. The accumulated data can be referred as a basis for demonstrating the consistence of pARM and the former ARM, and used in future research to augment the understanding of stress-induced emotional aggression in mice.

John Bishara,1 Thomas G Keens,1,2 Iris A Perez1,2 1Division of Pediatric Pulmonology and Sleep Medicine, Children’s Hospital Los Angeles, Los Angeles, CA, USA; 2Department of Pediatrics, Keck School of Medicine of USC, Los Angeles, CA, USA Abstract: Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder of the autonomic nervous system (ANS) and respiratory control. This disorder, formerly referred to as Ondine’s curse, is due to a mutation in the PHOX2B gene that affects the development of the neural crest cells. CCHS has an autosomal dominant pattern of inheritance. Majority of the patients have a polyalanine repeat mutation (PARM) of the PHOX2B, while a small group has non-PARM (NPARM). Knowledge of the patient’s PHOX2B gene mutation helps predict a patient’s clinical presentation and outcome and aids in anticipatory management of the respiratory and ANS dysfunction. Keywords: diaphragm pacing, noninvasive positive pressure ventilation, genetic counseling, genetic testing, CCHS, PHOX2B, congenital central hypoventilation syndrome

To ensure inheritance by daughter cells, many low-copy number bacterial plasmids, including the R1 drug-resistance plasmid, encode their own DNA segregation systems. The par operon of plasmid R1 directs construction of a simple spindle structure that converts free energy of polymerization of an actin-like protein, ParM, into work required to move sister plasmids to opposite poles of rod-shaped cells. The structures of individual components have been solved, but little is known about the ultrastructure of the R1 spindle. To determine the number of ParM filaments in a minimal R1 spindle, we used DNA-gold nanocrystal conjugates as mimics of the R1 plasmid. Wefound that each end of a single polar ParM filament binds to a single ParR/parC-gold complex, consistent with the idea that ParM filaments bind in the hollow core of the ParR/parC ring complex. Our results further suggest that multifilament spindles observed in vivo are associated with clusters of plasmids segregating as a unit.

Structural biology has experienced several transformative technological advances in recent years. These include: development of extremely bright X‐ray sources (microfocus synchrotron beamlines and free electron lasers) and the use of electrons to extend protein crystallography to ever decreasing crystal sizes; and an increase in the resolution attainable by cryo‐electron microscopy. Here we discuss the use of these techniques in general terms and highlight their application for biological filament systems, an area that is severely underrepresented in atomic resolution structures. We assemble a model of a capped tropomyosin‐actin minifilament to demonstrate the utility of combining structures determined by different techniques. Finally, we survey the methods that attempt to transform high resolution structural biology into more physiological environments, such as the cell. Together these techniques promise a compelling decade for structural biology and, more importantly, they will provide exciting discoveries in understanding the designs and purposes of biological machines. [ABSTRACT FROM AUTHOR]

From yeast to man, an evolutionary distance of 1.3 billion years, the F-actin filament structure has been conserved largely in line with the 94% sequence identity. The situation is entirely different in bacteria. In comparison to eukaryotic actins, the bacterial actin-like proteins (ALPs) show medium to low levels of sequence identity. This is extreme in the case of the ParM family of proteins, which often display less than 20% identity. ParMs are plasmid segregation proteins that form the polymerizing motors that propel pairs of plasmids to the extremities of a cell prior to cell division, ensuring faithful inheritance of the plasmid. Recently, exotic ParM filament structures have been elucidated that show ParM filament geometries are not limited to the standard polar pair of strands typified by actin. Four-stranded non-polar ParM filaments existing as open or closed nanotubules are found in Clostridium tetani and Bacillus thuringiensis, respectively. These diverse architectures indicate that the actin fold is capable of forming a large variety of filament morphologies, and that the conception of the “actin” filament has been heavily influenced by its conservation in eukaryotes. Here, we review the history of the structure determination of the eukaryotic actin filament to give a sense of context for the discovery of the new ParM filament structures. We describe the novel ParM geometries and predict that even more complex actin-like filaments may exist in bacteria. Finally, we compare the architectures of filaments arising from the actin and tubulin folds and conclude that the basic units possess similar properties that can each form a range of structures. Thus, the use of the actin fold in microfilaments and the tubulin fold for microtubules likely arose from a wider range of filament possibilities, but became entrenched as those architectures in early eukaryotes.

Clostridium perfringens produces an extensive repertoire of toxins and extracellular enzymes, many of which are intimately involved in the progression of disease and are encoded by genes on conjugative plasmids. In addition, many C. perfringens strains can carry up to five of these conjugative toxin or antimicrobial resistance plasmids, each of which has a similar 35 kb backbone. This conserved backbone includes the tcp conjugation locus and the central control region (CCR), which encodes genes involved in plasmid regulation, replication and partitioning, including a parMRC partitioning locus. Most conjugative plasmids in C. perfringens have a conserved replication protein, raising questions as to how multiple, closely related plasmids are maintained within a single strain. Bioinformatics analysis has highlighted the presence of at least 10 different parMRC partitioning system families ( parMRC A – J ) in these plasmids, with differences in amino acid sequence identity between each ParM family ranging from 15% to 54%. No two plasmids that encode genes belonging to the same partitioning family have been observed in a single strain, suggesting that these families represent the basis for plasmid incompatibility. In an attempt to validate the proposed parMRC incompatibility groups, genetically marked C. perfringens plasmids encoding identical parMRC C or parMRC D homologues or different combinations of parMRC A , parMRC C and parMRC D family homologues were introduced into a single strain via conjugation. The stability of each plasmid was determined using an incompatibility assay in which the plasmid profile of each strain was monitored over the course of two days in the absence of direct selection. The results showed that plasmids with identical parMRC C or parMRC D homologues were incompatible and could not coexist in the absence of external selection. By contrast, plasmids that encoded different parMRC homologues were compatible and could coexist in the same cell in the absence of selection, with the exception of strains housing parMRC C and parMRC D combinations, which showed a minor incompatibility phenotype. In conclusion, we have provided the first direct evidence of plasmid incompatibility in Clostridium spp. and have shown experimentally that the compatibility of conjugative C. perfringens plasmids correlates with the presence of parMRC -like partitioning systems of different phylogenetic subfamilies. [ABSTRACT FROM AUTHOR]

The Aggressive Response Meter (ARM) has been validated for measuring emotional (psychotic) aggression triggered by mental irritation in mice. In the present article, we newly developed a device, pARM (PowerLab-compatible type ARM). We collected on the aggressive biting behavior (ABB) intensity and ABB frequency of 20 male and female mice of ddY strain studied over a period of 6 days by using pARM and the former ARM. We calculated Pearson's correlation between the values of pARM and those of ARM. The accumulated data can be referred as a basis for demonstrating the consistence of pARM and the former ARM, and used in future research to augment the understanding of stress-induced emotional aggression in mice., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Author(s).)

Here we report the discovery of a bacterial DNA-segregating actinlike protein (BtParM) from Bacillus thuringiensis, which forms novel antiparallel, two-stranded, supercoiled, nonpolar helical filaments, as determined by electronmicroscopy. The BtParMfilament features of supercoiling and forming antiparallel double-strands are unique within the actin fold superfamily, and entirely different to the straight, double-stranded, polar helical filaments of all other known ParMs and of eukaryotic F-actin. The BtParM polymers show dynamic assembly and subsequent disassembly in the presence of ATP. BtParR, the DNA-BtParM linking protein, stimulated ATP hydrolysis/phosphate release by BtParM and paired two supercoiled BtParM filaments to form a cylinder, comprised of four strands with inner and outer diameters of 57 Å and 145 Å, respectively. Thus, in this prokaryote, the actin fold has evolved to produce a filament system with comparable features to the eukaryotic chromosomesegregating microtubule. [ABSTRACT FROM AUTHOR]

Background: Clinical practice guidelines need to be regularly updated with current literature in order to remain relevant. This paper reports on the approach taken by the Philippine Academy of Rehabilitation Medicine (PARM). This dovetails with its writing guide, which underpinned its foundational work in contextualizing guidelines for stroke and low back pain (LBP) in 2011. Methods: Working groups of Filipino rehabilitation physicians and allied health practitioners met to reconsider and modify, where indicated, the 'typical' Filipino patient care pathways established in the foundation guidelines. New clinical guidelines on stroke and low back pain which had been published internationally in the last 3 years were identified using a search of electronic databases. The methodological quality of each guideline was assessed using the iCAHE Guideline Quality Checklist, and only those guidelines which provided full text references, evidence hierarchy and quality appraisal of the included literature, were included in the PARM update. Each of the PARM-endorsed recommendations was then reviewed, in light of new literature presented in the included clinical guidelines. A novel standard updating approach was developed based on the criteria reported by Johnston et al. (Int J Technol Assess Health Care 19(4):646-655, 2003) and then modified to incorporate wording from the foundational PARM writing guide. The new updating tool was debated, pilot-tested and agreed upon by the PARM working groups, before being applied to the guideline updating process. Results: Ten new guidelines on stroke and eleven for low back pain were identified. Guideline quality scores were moderate to good, however not all guidelines comprehensively linked the evidence body underpinning recommendations with the literature. Consequently only five stroke and four low back pain guidelines were included. The modified PARM updating guide was applied by all working groups to ensure standardization of the wording of updated recommendations and the underpinning evidence bases. Conclusions: The updating tool provides a simple, standard and novel approach that incorporates evidence hierarchy and quality, and wordings of recommendations. It could be used efficiently by other guideline updaters particularly in developing countries, where resources for guideline development and updates are limited. When many people are involved in guideline writing, there is always the possibility of 'slippage' in use of wording and interpretation of evidence. The PARM updating tool provides a mechanism for maintaining a standard process for guideline updating processes that can be followed by clinicians with basic training in evidence-based practice principles. [ABSTRACT FROM AUTHOR]

Many pathogenic strains of Clostridium perfringens carry several highly similar toxin or antibiotic resistance plasmids that have 35 to 40 kb of very closely related syntenous sequences, including regions that carry the genes encoding conjugative transfer, plasmid replication and plasmid maintenance functions. Key questions are how are these closely related plasmids stably maintained in the same cell and what is the basis for plasmid incompatibility in C. perfringens . Comparative analysis of the Rep proteins encoded by these plasmids suggested that this protein was not the basis for plasmid incompatibility since plasmids carried in a single strain often encoded an almost identical Rep protein. These plasmids all carried a similar, but not identical, parMRC plasmid partitioning locus. Phylogenetic analysis of the deduced ParM proteins revealed that these proteins could be divided into ten separate groups. Importantly, in every strain that carried more than one of these plasmids, the respective ParM proteins were from different phylogenetic groups. Similar observations were made from the analysis of phylogenetic trees of the ParR proteins and the parC loci. These findings provide evidence that the basis for plasmid incompatibility in the conjugative toxin and resistance plasmid family from C. perfringens resides in subtle differences in the parMRC plasmid partitioning loci carried by these plasmids. [ABSTRACT FROM AUTHOR]

This study aimed to develop a self-report questionnaire to explore parental modelling of eating behaviours and then to use the newly developed measure to investigate associations between parental modelling with healthy and unhealthy food intake in both mothers and their children. Mothers ( n = 484) with a child aged between 18 months and 8 years completed the Parental Modelling of Eating Behaviours Scale ( PARM), a new, self-report measure of modelling, as well as a food frequency questionnaire. Principal components analysis of the PARM identified 15 items grouped into three subscales: verbal modelling (modelling through verbal communication); unintentional modelling ( UM) (children adopting eating behaviours that parents had not actively modelled); and behavioural consequences (children's eating behaviours directly associated with parental modelling). The PARM subscales were found to be differentially related to food intake. Maternally perceived consequences of behavioural modelling were related to increased fruit and vegetable intake in both mothers and children. UM was related to higher levels of savoury snack intake in both mothers and their children. This study has highlighted three distinct aspects of parental modelling of eating behaviours. The findings suggest that mothers may intentionally model healthy food intake while unintentionally acting as role models for their children's less healthy, snack food intake. [ABSTRACT FROM AUTHOR]

A brief history of the creation of a local museum in a former mining area; highlights the role of a local association for the protection of heritage (PARM) in his recovery and in museological idealization; having adopted a management model of partnership with the local government, it is the balance between what was possible and the constraints encountered. [ABSTRACT FROM AUTHOR]

Background: High-quality evidence-based clinical guidelines are widely available for many diseases. Clinical guidelines support evidence-based care decisions and improved health outcomes. Most clinical practice guidelines have been developed in the Western world and reflect a developed country's health systems and services, disease epidemiology, and workforce. Such guidelines are therefore not immediately relevant or generalizable to developing countries. Guidelines are expensive to produce, and it is more resource efficient for developing countries to contextualize available Western guidelines, rather than develop their own. This paper describes a leadership initiative by the Philippines Association of Rehabilitation Medicine to contextualize high-quality relevant Western guidelines for local management of stroke and low back pain. Methods: Twenty-one steps were developed, covering initial training and establishing the framework within which recommendations were contextualized; then guideline searching, critiquing, and including; and then contextualization, review, and implementation. A writing guide assisted the group to endorse recommendations in a standard manner, relevant to a "typical" patient journey, and to contextualize recommendations for local settings. Results: Recommendations were extracted from eight low back pain and five stroke clinical guidelines. Philippines Association of Rehabilitation Medicine endorsements were made, reflecting summarized recommendations and underpinning strength of the evidence body. Philippines Association of Rehabilitation Medicine context points contextualized the recommendations in terms of local health service delivery. Conclusion: A systematic reproducible process was applied to contextualize high-quality, relevant Western guidelines for immediate application to one developing country. This approach focused resources on contextualization, implementation, and uptake rather than de novo development. This leadership initiative offers a resource efficient way to implement evidence-based practice in developing countries when there is neither time nor resources for de novo guideline development. [ABSTRACT FROM AUTHOR]

Bacteria, like eukaryotes, employ cytoskeletal elements to perform many functions, including cell morphogenesis, cell division, DNA partitioning, and cell motility. They not only possess counterparts of eukaryotic actin, tubulin, and intermediate filament proteins, but they also have cytoskeletal elements of their own. Unlike the rigid sequence and structural conservation often observed for eukaryotic cytoskeletal proteins, the bacterial counterparts can display considerable diversity in sequence and function across species. Their wide range of function highlights the flexibility of core cytoskeletal protein motifs, such that one type of cytoskeletal element can perform various functions, and one function can be performed by different types of cytoskeletal elements. [ABSTRACT FROM AUTHOR]

Non-essential extra-chromosomal DNA elements such as plasmids are responsible for their own propagation in dividing host cells, and one means to ensure this is to carry a miniature active segregation system reminiscent of the mitotic spindle. Plasmids that are maintained at low numbers in prokaryotic cells have developed a range of such active partitioning systems, which are characterized by an impressive simplicity and efficiency and which are united by the use of dynamic, nucleotide-driven filaments to separate and position DNA molecules. A comparison of different plasmid segregation systems reveals (i) how unrelated filament-forming and DNA-binding proteins have been adopted and modified to create a range of simple DNA segregating complexes and (ii) how subtle changes in the few components of these DNA segregation machines has led to a remarkable diversity in the molecular mechanisms of closely related segregation systems. Here, our current understanding of plasmid segregation systems is reviewed and compared with other DNA segregation systems, and this is extended by a discussion of basic principles of plasmid segregation systems, evolutionary implications and the relationship between an autonomous DNA element and its host cell. [ABSTRACT FROM AUTHOR]

Abstract: The actin homolog ParM plays a microtubule-like role in segregating DNA prior to bacterial cell division. Fluorescence and cryo-electron microscopy have shown that ParM forms filament bundles between separating DNA plasmids in vivo. Given the lack of ParM bundling proteins it remains unknown how ParM bundles form at the molecular level. Here we show using time-lapse TIRF microscopy, under in vitro molecular crowding conditions, that ParM-bundle formation consists of two distinct phases. At the onset of polymerization bundle thickness and shape are determined in the form of nuclei of short helically disordered filaments arranged in a liquid-like lattice. These nuclei then undergo an elongation phase whereby they rapidly increase in length. At steady state, ParM bundles fuse into one single large aggregate. This behavior had been predicted by theory but has not been observed for any other cytomotive biopolymer, including F-actin. We employed electron micrographs of ParM rafts, which are 2-D analogs of 3-D bundles, to identify the main molecular interfilament contacts within these suprastructures. The interface between filaments is similar for both parallel and anti-parallel orientations and the distribution of filament polarity is random within a bundle. We suggest that the interfilament interactions are not due to the interactions of specific residues but rather to long-range, counter ion mediated, electrostatic attractive forces. A randomly oriented bundle ensures that the assembly is rigid and that DNA may be captured with equal efficiency at both ends of the bundle via the ParR binding protein. [Copyright &y& Elsevier]

Abstract: The basic features of the active filaments that use nucleotide hydrolysis to organise the cytoplasm are remarkably similar in the majority of all cells and are either actin-like or tubulin-like. Nearly all prokaryotic cells contain at least one form of FtsZ, the prokaryotic homologue of tubulin and some bacterial plasmids use tubulin-like TubZ for segregation. The other main family of active filaments, assembled from actin-like proteins, occurs in a wide range of bacterial species as well as in all eukaryotes. Some bacterial plasmids also use ParM, another actin-like protein. Higher-order filament structures vary from simple to complex depending on the cellular application. Equally, filament-associated proteins vary greatly between species and it is not possible currently to trace their evolution from prokaryotes to eukaryotes. This lack of similarity except in the three-dimensional structures and longitudinal interactions between the filament subunits hints that the most basic cellular function of the filaments is to act as linear motors driven by assembly dynamics and/or bending and hence we term these filament systems ‘cytomotive’. The principle of cytomotive filaments seems to have been invented independently for actin- and tubulin-like proteins. Prokaryotes appear to have a third class of cytomotive filaments, typically associated with surfaces such as membranes or DNA: Walker A cytoskeletal ATPases (WACA). A possible evolutionary relationship of WACAs with eukaryotic septins is discussed. [Copyright &y& Elsevier]

The R1 plasmid employs ATP-driven polymerisation of the actin-like protein ParM to move newly replicated DNA to opposite poles of a bacterial cell. This process is essential for ensuring accurate segregation of the low-copy number plasmid and is the best characterised example of DNA partitioning in prokaryotes. In vivo, ParM only forms long filaments when capped at both ends by attachment to a centromere-like region parC, through a small DNA-binding protein ParR. Here, we present biochemical and electron microscopy data leading to a model for the mechanism by which ParR–parC complexes bind and stabilise elongating ParM filaments. We propose that the open ring formed by oligomeric ParR dimers with parC DNA wrapped around acts as a rigid clamp, which holds the end of elongating ParM filaments while allowing entry of new ATP-bound monomers. We propose a processive mechanism by which cycles of ATP hydrolysis in polymerising ParM drives movement of ParR-bound parC DNA. Importantly, our model predicts that each pair of plasmids will be driven apart in the cell by just a single double helical ParM filament. [ABSTRACT FROM AUTHOR]

ParM is a prokaryotic actin homologue, which ensures even plasmid segregation before bacterial cell division. In vivo, ParM forms a labile filament bundle that is reminiscent of the more complex spindle formed by microtubules partitioning chromosomes in eukaryotic cells. However, little is known about the underlying structural mechanism of DNA segregation by ParM filaments and the accompanying dynamic instability. Our biochemical, TIRF microscopy and high-pressure SAX observations indicate that polymerization and disintegration of ParM filaments is driven by GTP rather than ATP and that ParM acts as a GTP-driven molecular switch similar to a G protein. Image analysis of electron micrographs reveals that the ParM filament is a left-handed helix, opposed to the right-handed actin polymer. Nevertheless, the intersubunit contacts are similar to those of actin. Our atomic model of the ParM-GMPPNP filament, which also fits well to X-ray fibre diffraction patterns from oriented gels, can explain why after nucleotide release, large conformational changes of the protomer lead to a breakage of intra- and interstrand interactions, and thus to the observed disintegration of the ParM filament after DNA segregation. [ABSTRACT FROM AUTHOR]

Abstract: Using in vitro TIRF- and electron-microscopy, we reinvestigated the dynamics of native ParM, a prokaryotic DNA segregation protein and actin homolog. In contrast to a previous study, which used a cysteine ParM mutant, we find that the polymerization process of wild type ATP-ParM filaments consists of a polymerization phase and a subsequent steady state phase, which is dynamically unstable, like that of microtubules. We find that the apparent bidirectional polymerization of ParM, is not due to the intrinsic nature of this filament, but results from ParM forming randomly oriented bundles in the presence of crowding agents. Our results imply, that in the bacterium, ParM filaments spontaneously form bipolar bundles. Due to their intrinsic dynamic instability, ParM bundles can efficiently “search” the cytoplasmic lumen for DNA, bind it equally well at the bipolar ends and segregate it approximately symmetrically, by the insertion of ParM subunits at either end. [Copyright &y& Elsevier]

Bacterial cells contain a variety of structural filamentous proteins necessary for the spatial regulation of cell shape, cell division, and chromosome segregation, analogous to the eukaryotic cytoskeletal proteins. The molecular mechanisms by which these proteins function are beginning to be revealed, and these proteins show numerous three-dimensional structural features and biochemical properties similar to those of eukaryotic actin and tubulin, revealing their evolutionary relationship. Recent technological advances have illuminated links between cell division and chromosome segregation, suggesting a higher complexity and organization of the bacterial cell than was previously thought. [ABSTRACT FROM AUTHOR]

Prokaryotic homologs of the eukaryotic structural protein actin, such as MreB and ParM, have been implicated in determination of bacterial cell shape, and in the segregation of genomic and plasmid DNA. In contrast to these bacterial actin homologs, little is known about the archaeal counterparts. As a first step, we expressed a predicted actin homolog of the thermophilic archaeon Thermoplasma acidophilum, Ta0583, and determined its crystal structure at 2.1Å resolution. Ta0583 is expressed as a soluble protein in T.acidophilum and is an active ATPase at physiological temperature. In vitro, Ta0583 forms sheets with spacings resembling the crystal lattice, indicating an inherent propensity to form filamentous structures. The fold of Ta0583 contains the core structure of actin and clearly belongs to the actin/Hsp70 superfamily of ATPases. Ta0583 is approximately equidistant from actin and MreB on the structural level, and combines features from both eubacterial actin homologs, MreB and ParM. The structure of Ta0583 co-crystallized with ADP indicates that the nucleotide binds at the interface between the subdomains of Ta0583 in a manner similar to that of actin. However, the conformation of the nucleotide observed in complex with Ta0583 clearly differs from that in complex with actin, but closely resembles the conformation of ParM-bound nucleotide. On the basis of sequence and structural homology, we suggest that Ta0583 derives from a ParM-like actin homolog that was once encoded by a plasmid and was transferred into a common ancestor of Thermoplasma and Ferroplasma. Intriguingly, both genera are characterized by the lack of a cell wall, and therefore Ta0583 could have a function in cellular organization. [Copyright &y& Elsevier]

Bacterial plasmids encode partitioning (par) loci that ensure ordered plasmid segregation prior to cell division. par loci come in two types: those that encode actin-like ATPases and those that encode deviant Walker-type ATPases. ParM, the actin-like ATPase of plasmid R1, forms dynamic filaments that segregate plasmids paired at mid-cell to daughter cells. Like microtubules, ParM filaments exhibit dynamic instability (i.e., catastrophic decay) whose regulation is an important component of the DNA segregation process. The Walker box ParA ATPases are related to MinD and form highly dynamic, oscillating filaments that are required for the subcellular movement and positioning of plasmids. The role of the observed ATPase oscillation is not yet understood. However, we propose a simple model that couples plasmid segregation to ParA oscillation. The model is consistent with the observed movement and localization patterns of plasmid foci and does not require the involvement of plasmid-specific host-encoded factors. [ABSTRACT FROM AUTHOR]

In order to isolate magnetic signals carried by single-domain (SD) ferrimagnetic (FM) minerals from multi-domain (MD) FM minerals, we developed a few parameters using partial anhysteretic remanent magnetization (pARM). Because MD fraction contains only soft (easy to be demagnetized) coercivity spectrum, pARM(>20 mT) was sensitive in eliminating MD contributions. Ratio of pARM(5 mT, 10 mT)/pARM(0, 5 mT) is useful in quantifying a relative abundance of mass ratio between SD and MD fractions. These new proxies can quickly characterize the details of grain size distribution of magnetic minerals in paleoclimatic and paleomagnetic studies. [ABSTRACT FROM AUTHOR]

Actin participates in many important biological processes. Currently, intensive investigation is being carried out in a number of laboratories concerning the function of actin in these processes and the molecular basis of its functions. We present a glimpse into four of these areas: actin-like proteins in bacterial cells, actin in the eukaryotic nucleus, the conformational plasticity of the actin filament, and finally, Arp2/3-dependent regulation of actin filament branching and creation of new filament barbed ends. IUBMB Life , 57: 683–687, 2005 [ABSTRACT FROM AUTHOR]

The structural elucidation of clear but distant homologs of actin and tubulin in bacteria and GFP labeling of these proteins promises to reinvigorate the field of prokaryotic cell biology. FtsZ (the tubulin homolog) and MreB/ParM (the actin homologs) are indispensable for cellular tasks that require the cell to accurately position molecules, similar to the function of the eukaryotic cytoskeleton. FtsZ is the organizing molecule of bacterial cell division and forms a filamentous ring around the middle of the cell. Many molecules, including MinCDE, SulA, ZipA, and FtsA, assist with this process directly. Recently, genes much more similar to tubulin than to FtsZ have been identified in Verrucomicrobia. MreB forms helices underneath the inner membrane and probably defines the shape of the cell by positioning transmembrane and periplasmic cell wall--synthesizing enzymes. Currently, no interacting proteins are known for MreB and its relatives that help these proteins polymerize or depolymerize at certain times and places inside the cell. It is anticipated that MreB-interacting proteins exist in analogy to the large number of actin binding proteins in eukaryotes. ParM (a plasmid-borne actin homolog) is directly involved in pushing certain single-copy plasmids to the opposite poles by ParR/parC-assisted polymerization into double-helical filaments, much like the filaments formed by actin, F-actin. Mollicutes seem to have developed special systems for cell shape determination and motility, such as the fibril protein in Spiroplasma. [ABSTRACT FROM AUTHOR]

The mechanisms responsible for prokaryotic DNA segregation are largely unknown. The partitioning locus (par) encoded by the Escherichia coli plasmid R1 actively segregates its replicon to daughter cells. We show here that the ParM ATPase encoded by par forms dynamic actin‐like filaments with properties expected for a force‐generating protein. Filament formation depended on the other components encoded by par, ParR and the centromere‐like parC region to which ParR binds. Mutants defective in ParM ATPase exhibited hyperfilamentation and did not support plasmid partitioning. ParM polymerization was ATP dependent, and depolymerization of ParM filaments required nucleotide hydrolysis. Our in vivo and in vitro results indicate that ParM polymerization generates the force required for directional movement of plasmids to opposite cell poles and that the ParR–parC complex functions as a nucleation point for ParM polymerization. Hence, we provide evidence for a simple prokaryotic analogue of the eukaryotic mitotic spindle apparatus. [ABSTRACT FROM AUTHOR]

The mechanisms responsible for prokaryotic DNA segregation are largely unknown. The partitioning locus (par) encoded by the Escherichia coli plasmid R1 actively segregates its replicon to daughter cells. We show here that the ParM ATPase encoded by par-forms dynamic actin-like filaments with properties expected for a force-generating protein. Filament formation depended on the other components encoded by par, ParR and the centromere-like parC region to which ParR binds. Mutants defective in ParM ATPase exhibited hyperfilamentation and did not support plasmid partitioning. ParM polymerization was ATP dependent, and depolymerization of ParM filaments required nucleotide hydrolysis. Our in vivo and in vitro results indicate that ParM polymerization generates the force required for directional movement of plasmids to opposite cell poles and that the ParR-parC complex functions as a nucleation point for ParM polymerization. Hence, we provide evidence for a simple prokaryotic analogue of the eukaryotic mitotic spindle apparatus. [ABSTRACT FROM AUTHOR]

Abstract Background Recently, contradictory results on foamy virus protease activity were published. While our own results indicated that protease activity is regulated by the viral RNA, others suggested that the integrase is involved in the regulation of the protease. Results To solve this discrepancy we performed additional experiments showing that the protease-reverse transcriptase (PR-RT) exhibits protease activity in vitro and in vivo, which is independent of the integrase domain. In contrast, Pol incorporation, and therefore PR activity in the viral context, is dependent on the integrase domain. To further analyse the regulation of the protease, we incorporated Pol in viruses by expressing a GagPol fusion protein, which supported near wild-type like infectivity. A GagPR-RT fusion, lacking the integrase domain, also resulted in wild-type like Gag processing, indicating that the integrase is dispensable for viral Gag maturation. Furthermore, we demonstrate with a trans-complementation assays that the PR in the context of the PR-RT protein supports in trans both, viral maturation and infectivity. Conclusion We provide evidence that the FV integrase is required for Pol encapsidation and that the FV PR activity is integrase independent. We show that an active PR can be encapsidated in trans as a GagPR-RT fusion protein.

Abstract: The bacterial actin homolog ParM has always been modeled as a polar filament, comprising two parallel helical strands, like actin itself. I present arguments here that ParM may be an apolar filament, in which the two helical strands are antiparallel. [Copyright &y& Elsevier]

A biomimetic system capable of replication and segregation of genetic material constitutes an essential component for the future design of a minimal synthetic cell. Here we have used the simple T7 bacteriophage system and the plasmid-derived ParMRC system to establish in vitro DNA replication and DNA segregation, respectively. These processes were incorporated into biomimetic compartments providing an enclosed reaction space. The functional lifetime of the encapsulated segregation system could be prolonged by equipping it with ATP-regenerating and oxygen-scavenging systems. Finally, we showed that DNA replication and segregation processes could be coupled in vitro by using condensed DNA nanoparticles resulting from DNA replication. ParM spindles extended over tens of micrometers and could thus be used for segregation in compartments that are significantly longer than bacterial cell size. Overall, this work demonstrates the successful bottom-up assembly and coupling of molecular machines that mediate replication and segregation, thus providing an important step towards the development of a fully functional minimal cell., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

From yeast to man, an evolutionary distance of 1.3 billion years, the F-actin filament structure has been conserved largely in line with the 94% sequence identity. The situation is entirely different in bacteria. In comparison to eukaryotic actins, the bacterial actin-like proteins (ALPs) show medium to low levels of sequence identity. This is extreme in the case of the ParM family of proteins, which often display less than 20% identity. ParMs are plasmid segregation proteins that form the polymerizing motors that propel pairs of plasmids to the extremities of a cell prior to cell division, ensuring faithful inheritance of the plasmid. Recently, exotic ParM filament structures have been elucidated that show ParM filament geometries are not limited to the standard polar pair of strands typified by actin. Four-stranded non-polar ParM filaments existing as open or closed nanotubules are found inClostridium tetaniandBacillus thuringiensis, respectively. These diverse architectures indicate that the actin fold is capable of forming a large variety of filament morphologies, and that the conception of the “actin” filament has been heavily influenced by its conservation in eukaryotes. Here, we review the history of the structure determination of the eukaryotic actin filament to give a sense of context for the discovery of the new ParM filament structures. We describe the novel ParM geometries and predict that even more complex actin-like filaments may exist in bacteria. Finally, we compare the architectures of filaments arising from the actin and tubulin folds and conclude that the basic units possess similar properties that can each form a range of structures. Thus, the use of the actin fold in microfilaments and the tubulin fold for microtubules likely arose from a wider range of filament possibilities, but became entrenched as those architectures in early eukaryotes. [ABSTRACT FROM PUBLISHER]

As discovered over the past 25 years, the cytoskeletons of bacteria and archaea are complex systems of proteins whose central components are dynamic cytomotive filaments. They perform roles in cell division, DNA partitioning, cell shape determination and the organisation of intracellular components. The protofilament structures and polymerisation activities of various actin-like, tubulin-like and ESCRT-like proteins of prokaryotes closely resemble their eukaryotic counterparts but show greater diversity. Their activities are modulated by a wide range of accessory proteins but these do not include homologues of the motor proteins that supplement filament dynamics to aid eukaryotic cell motility. Numerous other filamentous proteins, some related to eukaryotic IF-proteins/lamins and dynamins etc, seem to perform structural roles similar to those in eukaryotes.

One of the well-known functions of the bacterial cytoskeleton is plasmid segregation. Type II plasmid segregation systems, among the best characterized with respect to the mechanism of action, possess an actin-like cytomotive filament as the motor component. This chapter describes the essential components of the plasmid segregation machinery and their mechanism of action, concentrating on the actin-like protein family of the bacterial cytoskeleton. The structures of the actin-like filaments depend on their nucleotide state and these in turn contribute to the dynamics of the filaments. The components that link the filaments to the plasmid DNA also regulate filament dynamics. The modulation of the dynamics facilitates the cytomotive filament to function as a mitotic spindle with a minimal number of components.

Here we report the discovery of a bacterial DNA-segregating actin-like protein (BtParM) from Bacillus thuringiensis, which forms novel antiparallel, two-stranded, supercoiled, nonpolar helical filaments, as determined by electron microscopy. The BtParM filament features of supercoiling and forming antiparallel double-strands are unique within the actin fold superfamily, and entirely different to the straight, double-stranded, polar helical filaments of all other known ParMs and of eukaryotic F-actin. The BtParM polymers show dynamic assembly and subsequent disassembly in the presence of ATP. BtParR, the DNA-BtParM linking protein, stimulated ATP hydrolysis/phosphate release by BtParM and paired two supercoiled BtParM filaments to form a cylinder, comprised of four strands with inner and outer diameters of 57 Å and 145 Å, respectively. Thus, in this prokaryote, the actin fold has evolved to produce a filament system with comparable features to the eukaryotic chromosome-segregating microtubule.