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Partially charged chiral molecules act as spin filters, with preference for electron transport toward one type of spin ("up" or "down"), depending on their handedness. This effect is named the chiral induced spin selectivity (CISS) effect. A consequence of this phenomenon is spin polarization concomitant with electric polarization in chiral molecules. These findings were shown by adsorbing chiral molecules on magnetic surfaces and investigating the spin-exchange interaction between the surface and the chiral molecule. This field of study was developed using artificial chiral molecules. Here we used such magnetic surfaces to explore the importance of the intrinsic chiral properties of proteins in determining their stability. First, proteins were adsorbed on paramagnetic and ferromagnetic nanoparticles in a solution, and subsequently urea was gradually added to induce unfolding. The structural stability of proteins was assessed using two methods: bioluminescence measurements used to monitor the activity of the Luciferase enzyme, and fast spectroscopy detecting the distance between two chromophores implanted at the termini of a Barnase core. We found that interactions with magnetic materials altered the structural and functional resilience of the natively folded proteins, affecting their behavior under varying mild denaturing conditions. Minor structural disturbances at low urea concentrations were impeded in association with paramagnetic nanoparticles, whereas at higher urea concentrations, major structural deformation was hindered in association with ferromagnetic nanoparticles. These effects were attributed to spin exchange interactions due to differences in the magnetic imprinting properties of each type of nanoparticle. Additional measurements of proteins on macroscopic magnetic surfaces support this conclusion. The results imply a link between internal spin exchange interactions in a folded protein and its structural and functional integrity on magnetic surfaces. Together with the accumulating knowledge on CISS, our findings suggest that chirality and spin exchange interactions should be considered as additional factors governing protein structures. [ABSTRACT FROM AUTHOR]

In eukaryotes, Hsp110s are unambiguous cognates of the Hsp70 chaperones, in primary sequence, domain organization, and structure. Hsp110s function as nucleotide exchange factors (NEFs) for the Hsp70s although their apparent loss of Hsp70‐like chaperone activity, nature of interdomain communication, and breadth of domain functions are still puzzling. Here, by combining single‐molecule FRET, small angle X‐ray scattering measurements (SAXS), and MD simulation, we show that yeast Hsp110, Sse1 lacks canonical Hsp70‐like interdomain allostery. However, the protein exhibits unique noncanonical conformational changes within its domains. Sse1 maintains an open‐lid substrate‐binding domain (SBD) in close contact with its nucleotide‐binding domain (NBD), irrespective of its ATP hydrolysis status. To further appreciate such ATP‐hydrolysis‐independent exhaustive interaction between two domains of Hsp110s, NBD‐SBD chimera was constructed between Hsp110 (Sse1) and Hsp70 (Ssa1). In Sse1/Ssa1 chimera, we observed undocking of two domains leading to complete loss of NEF activity of Sse1. Interestingly, chimeric proteins exhibited significantly enhanced ATPase rate of Sse1‐NBD compared to wild‐type protein, implying that intrinsic ATPase activity of the protein remains mostly repressed. Apart from repressing the high ATPase activity of its NBD, interactions between two domains confer thermal stability to Sse1 and play critical role in the (co)chaperoning function of Sse1 in Ssa1‐mediated disaggregation activity. Altogether, Sse1 exhibits a unique interdomain interaction, which is essential for its NEF activity, suppression of high intrinsic ATPase activity, co‐chaperoning activity in disaggregase machinery, and stability of the protein. [ABSTRACT FROM AUTHOR]

Many proteins comprising of complex topologies require molecular chaperones to achieve their unique three-dimensional folded structure. The E.coli chaperone, GroEL binds with a large number of unfolded and partially folded proteins, to facilitate proper folding and prevent misfolding and aggregation. Although the major structural components of GroEL are well defined, scaffolds of the non-native substrates that determine chaperone-mediated folding have been difficult to recognize. Here we performed all-atomistic and replica-exchange molecular dynamics simulations to dissect non-native ensemble of an obligate GroEL folder, DapA. Thermodynamics analyses of unfolding simulations revealed populated intermediates with distinct structural characteristics. We found that surface exposed hydrophobic patches are significantly increased, primarily contributed from native and non-native β-sheet elements. We validate the structural properties of these conformers using experimental data, including circular dichroism (CD), 1-anilinonaphthalene-8-sulfonic acid (ANS) binding measurements and previously reported hydrogen-deutrium exchange coupled to mass spectrometry (HDX-MS). Further, we constructed network graphs to elucidate long-range intra-protein connectivity of native and intermediate topologies, demonstrating regions that serve as central “hubs”. Overall, our results implicate that genomic variations (or mutations) in the distinct regions of protein structures might disrupt these topological signatures disabling chaperone-mediated folding, leading to formation of aggregates. [ABSTRACT FROM AUTHOR]

The role of bacterial DnaJ protein as a cochaperone of DnaK is strongly appreciated. Although DnaJ unaccompanied by DnaK can bind unfolded as well as native substrate proteins, its rale as an individual chaperone remains elusive. In this study, we demonstrate that DnaJ binds a model non-native substrate with a low nanomolar dissociation constant and, more importantly, modulates the structure of its non-native state. The structural modulation achieved by DnaJ is different compared to that achieved by the DnaK-DnaJ complex. The nature of structural modulation exerted by DnaJ is suggestive of a unique unfolding activity on the non-native substrate by the chaperone. Furthermore, we demonstrate that the zinc binding motif along with the C-terminal substrate binding domain of DnaJ is necessary and sufficient for binding and the subsequent binding-Induced structural alterations of the non-native substrate. We hypothesize that this hitherto unknown structural alteration of non-native states by DnaJ might be important for its chaperoning activity by removing kinetic traps of the folding intermediates. [ABSTRACT FROM AUTHOR]

The growing number of missions has brought previously unapproachable and incomprehensible regions of the universe into the realm of our understanding. The millennial boosts in technological innovations have enabled us to expand the horizons of our exploration far beyond our immediate neighborhood in the solar system. As is inevitable for any scientific discovery of magnitude, to open up questions for further evaluations, recent space endeavors have necessitated the search for analogue sites on Earth that mimic these extraterrestrial sites in order to glean insights into physicochemical and geological processes, potential habitability and operational parameters for future missions[1]. Various analogue sites have been identified across the world on the basis of their resemblance to a celestial body of interest. These sites have been used to address questions pertaining to distinct fields of inquiry, i.e., the origin and evolution of life, habitability and biosignatures, in addition to the ground testing of several instruments to be used at these off-Earth locations. This study explores the role of one such analogue site, Ladakh. Ladakh is located in the Himalayan region, situated North of the Indian subcontinent. Located at elevations of 3,000-5,700m above sea level, its geographical location means that this region has been exposed to limited natural weathering and anthropogenic activities, as it is in the rain-shadow region and it is difficult to access. Furthermore, the high altitude nature of this region means that there is the challenge of the stressful conditions of cold temperatures, low oxygen partial pressure and high UV irradiation. Though testing in terms of survival, these geophysical features result in Ladakh being considered a suitable Mars analogue, sharing a low atmospheric pressure and a high UV index given the lack of magnetic activity and sparseness of its atmosphere. Scouted as part of the first NASA Spaceward Bound India (SBI) program of 2016, Ladakh offers the unique advantage of being an amalgamation of multiple extreme environments with astrobiological significance within the same region. The cold arid desert conditions of Ladakh harbor varied geological features and features of scientific interest, including glacial deposits, hot springs, sand dunes, salt crusts, permafrost regions, and saline lakes [2]. Each of these sites are characterized by distinct geological features that can help provide answers to fundamental questions pertaining to habitability (extremophilic microbes residing in hot springs with temperatures of 70°C to those surviving under permafrost conditions where the temperatures never rise above 0°C) and potential biosignatures that could be formed and preserved under conditions considered analogous to environments on Mars. The biogeochemical features, like the ionic composition and temperatures of hot springs environments, could be used to drive research towards the origin and subsequent evolution and diversification of the earliest life forms [3]. Moreover, the rugged terrain of Ladakh provides perfect grounds for the testing of rover and landing mission instruments, like the HABIT (HabitAbility, Brine Irradiation and Temperature), an instrument tested during the SBI 2016 expedition, which is used for evaluating the habitability and also explore the In-Situ Resource Utilization (ISRU) options for ExoMars mission [4]. Its field trial in Ladakh aimed at establishing its basic functional principle of capturing water on salt surfaces to create a brine, which may be relevant for future missions. With strong potential to act as an analogue site for Mars, Ladakh remains an enigma to be explored. [ABSTRACT FROM AUTHOR]

Life is a non-equilibrium phenomenon. Owing to their high free energy content, the macromolecules of life tend to spontaneously react with ambient oxygen and water and turn into more stable inorganic molecules. A similar thermodynamic picture applies to the complex shapes of proteins: While a polypeptide is emerging unfolded from the ribosome, it may spontaneously acquire secondary structures and collapse into its functional native conformation. The spontaneity of this process is evidence that the free energy of the unstructured state is higher than that of the structured native state. Yet, under stress or because of mutations, complex polypeptides may fail to reach their native conformation and form instead thermodynamically stable aggregates devoid of biological activity. Cells have evolved molecular chaperones to actively counteract the misfolding of stress-labile proteins dictated by equilibrium thermodynamics. HSP60, HSP70 and HSP100 can inject energy from ATP hydrolysis into the forceful unfolding of stable misfolded structures in proteins and convert them into unstable intermediates that can collapse into the native state, even under conditions inauspicious for that state. Aggregates and misfolded proteins may also be forcefully unfolded and degraded by chaperone-gated endo-cellular proteases, and in eukaryotes also by chaperone-mediated autophagy, paving the way for their replacement by new, unaltered functional proteins. The greater energy cost of degrading and replacing a polypeptide, with respect to the cost of its chaperone-mediated repair represents a thermodynamic dilemma: some easily repairable proteins are better to be processed by chaperones, while it can be wasteful to uselessly try recover overly compromised molecules, which should instead be degraded and replaced. Evolution has solved this conundrum by creating a host of unfolding chaperones and degradation machines and by tuning their cellular amounts and activity rates., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Fauvet, Rebeaud, Tiwari, De Los Rios and Goloubinoff.)

Understanding the folding pathway of any protein is of utmost importance for deciphering the folding problems under adverse conditions. We can obtain important information about the folding pathway by monitoring the folding of any protein from its unfolded state. It is usually very difficult to monitor the folding process in real time as the process is generally very fast, and we need a suitable read out. In this protocol, we have solved this issue by using a protein that is non-fluorescent in its unfolded state but fluoresces in its native state after folding. The kinetics of refolding can be monitored by following the increase in fluorescence in real time. Previously, this was generally achieved by either monitoring a protein's enzymatic activity or measuring the tryptophan fluorescence, where the signal output depends on well-described enzymatic activity or the frequency of tryptophan residues present in the proteins, respectively. Here, we describe a simple and real-time assay to monitor the refolding of sGFP, a recently described slow-folding mutant of yeGFP (yeast enhanced GFP). We unfold this protein using chemical denaturant and refold in a suitable buffer, monitoring the increase in fluorescence over time. GFP is fluorescent only when correctly folded; thus, using this technique, we can measure the true rate of protein refolding by following the increase in fluorescence over time. Therefore, sGFP can be used as an ideal model to study the in vitro protein folding process. Accordingly, the effects of different conditions and molecules on the protein folding pathway can be efficiently studied using sGFP as a model protein. Graphical abstract: Schematic of the steps involved in the sGFP refolding pathway. Native sGFP is unfolded by chemical denaturation using 6 M GuHCl at 25°C for 1 hour and then refolded in refolding buffer by 100-fold dilution., Competing Interests: Competing interestsThe authors declare no competing interests., (Copyright © 2021 The Authors; exclusive licensee Bio-protocol LLC.)

Mortality in COVID-19 patients predominantly results from an acute respiratory distress syndrome (ARDS), in which lungs alveolar cells undergo programmed cell death. Mortality in a sepsis-induced ARDS rat model is reduced by adenovirus over-expression of the HSP70 chaperone. A natural rise of body temperature during mild fever can naturally accumulate high cellular levels of HSP70 that can arrest apoptosis and protect alveolar lung cells from inflammatory damages. However, beyond 1-2 h of fever, no HSP70 is being further produced and a decreased in body temperature required to the restore cell's ability to produce more HSP70 in a subsequent fever cycle. We suggest that antipyretics may be beneficial in COVID-19 patients subsequent to several hours of mild (<38.8°C) advantageous fever, allowing lung cells to accumulate protective HSP70 against damages from the inflammatory response to the virus SARS-CoV-2. With age, the ability to develop fever and accumulate HSP70 decreases. This could be ameliorated, when advisable to do so, by thermotherapies and/or physical training., (Copyright © 2020 Guihur, Rebeaud, Fauvet, Tiwari, Weiss and Goloubinoff.)