Search

The ability to control locomotion in a dynamic environment provides a competitive advantage for microorganisms, thus driving the evolution of sophisticated regulatory systems. In total, 19 known categories of chemotaxis systems control motility mediated by flagella or Type IV pili, plus other cellular functions. A key feature that distinguishes chemotaxis systems from generic two‐component regulatory systems is separation of receptor and kinase functions into distinct proteins, linked by CheW scaffold proteins. This arrangement allows for formation of varied arrays with remarkable signaling properties. We recently analyzed sequences of CheW‐like domains found in CheA kinases and CheW and CheV scaffold proteins. In total, 16 Architectures of CheA, CheW, and CheV proteins contain ~94% of all CheW‐like domains and form six Classes with likely functional specializations. We surveyed chemotaxis system categories and proteins containing CheW‐like domains in ~1900 prokaryotic species, the most comprehensive analysis to date, revealing new insights. Co‐occurrence analyses suggested that many chemotaxis systems occur in non‐random combinations within species, implying synergy or antagonism. Furthermore, many Architectures of proteins containing CheW‐like domains occurred predominantly with specific categories of chemotaxis systems, suggesting specialized functional interactions. We propose Class 1 (~80%) and Class 6 (~20%) CheW proteins exhibit preferences for distinct chemoreceptor structures. Furthermore, rare (~1%) Class 2 CheW proteins frequently co‐occurred with methyl‐accepting coiled coil proteins, which contain both receptor and kinase functions and so do not require connection via a CheW scaffold but may benefit from arrays. Last, rare multidomain CheW proteins may interact with different receptors than single‐domain CheW proteins. [ABSTRACT FROM AUTHOR]

Domains are the three‐dimensional building blocks of proteins. An individual domain can occur in a variety of domain architectures that perform unique functions and are subject to different evolutionary selective pressures. We describe an approach to evaluate the variability in amino acid sequences of a single domain across architectural contexts. The ability to distinguish different evolutionary outcomes of one protein domain can help determine whether existing knowledge about a specific domain will apply to an uncharacterized protein, lead to insights and hypotheses about function, and guide experimental priorities. We developed and tested our approach on CheW‐like domains (PF01584), which mediate protein/protein interactions and are difficult to compare experimentally. CheW‐like domains occur in CheW scaffolding proteins, CheA kinases, and CheV proteins that regulate bacterial chemotaxis. We analyzed 16 domain architectures that included 94% of all CheW‐like domains found in nature. We identified six Classes of CheW‐like domains with presumed functional differences. CheV and most CheW proteins contained Class 1 domains, whereas some CheW proteins contained Class 6 (~20%) or Class 2 (~1%) domains instead. Most CheA proteins contained Class 3 domains. CheA proteins with multiple Hpt domains contained Class 4 domains. CheA proteins with two CheW‐like domains contained one Class 3 and one Class 5. We also created SimpLogo, an innovative method for visualizing amino acid composition across large sets of multiple sequence alignments of arbitrary length. SimpLogo offers substantial advantages over standard sequence logos for comparison and analysis of related protein sequences. The R package for SimpLogo is freely available. [ABSTRACT FROM AUTHOR]

Chemotaxis responses of Escherichia coli and Salmonella are mediated by type I membrane receptors with N-terminal extracytoplasmic sensing domains connected by transmembrane helices to C-terminal signaling domains in the cytoplasm. Receptor signaling involves regulation of an associated protein kinase, CheA. Here we show that kinase activation by a soluble signaling domain construct involves the formation of a large complex, with ∼14 receptor signaling domains per CheA dimer. Electron microscopic examination of these active complexes indicates a well defined bundle composed of numerous receptor filaments. Our findings suggest a mechanism for transmembrane signaling whereby stimulus-induced changes in lateral packing interactions within an array of receptor-sensing domains at the cell surface perturb an equilibrium between active and inactive receptor­kinase complexes within the cytoplasm. [ABSTRACT FROM AUTHOR]

The CheW protein plays a key role in bacterial chemotaxis signal transduction by coupling CheA to chemotaxis receptors. CheW from Thermotoga maritima has been overexpressed in Escherichia coli and crystallized at 298 K using ammonium sulfate as a salt precipitant. X-ray diffraction data have been collected to 3.10 Å resolution at 100 K using synchrotron radiation. The crystal belonged to space group P63, with unit-cell parameters a = b = 61.265, c = 361.045 Å. The asymmetric unit may contain four to six CheW molecules. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate the effect of oral rehabilitation using immediately loaded fixed implant-supported mandibular prostheses, considering chewing, swallowing, speech and voice aspects. Material and methods: Fourteen patients subjected to this treatment were evaluated by a clinical examination of the stomatognathic system and perceptual evaluation of voice quality before oral rehabilitation, as well as after 1 and 4 months. Results: After oral rehabilitation, the results showed that there were no significant modifications in the aspects investigated. Conclusion: Thus, implant-supported prosthetic rehabilitation, despite providing a more satisfactory occlusal standard, did not yield changes in the functional patterns of individuals in this study. [ABSTRACT FROM AUTHOR]