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From Proteopedia
X-ray structure of McpS ligand binding domain in complex with succinate
Structural highlights
FunctionMCPS_PSEPK Chemotactic-signal transducers respond to changes in the concentration of attractants and repellents in the environment, transduce a signal from the outside to the inside of the cell, and facilitate sensory adaptation through the variation of the level of methylation. McpS is a specific chemoreceptor for 6 tricarboxylic acid (TCA) cycle intermediates (succinate, fumarate, malate, oxaloacetate, citrate and isocitrate), butyrate and acetate. Malate, succinate, fumarate and oxaloacetate cause the strongest chemotactic response.[1] [2] Publication Abstract from PubMedChemoreceptor-based signaling is a central mechanism in bacterial signal transduction. Receptors are classified according to the size of their ligand-binding region. The well-studied cluster I proteins have a 100- to 150-residue ligand-binding region that contains a single site for chemoattractant recognition. Cluster II receptors, which contain a 220- to 300-residue ligand-binding region and which are almost as abundant as cluster I receptors, remain largely uncharacterized. Here, we report high-resolution structures of the ligand-binding region of the cluster II McpS chemotaxis receptor (McpS-LBR) of Pseudomonas putida KT2440 in complex with different chemoattractants. The structure of McpS-LBR represents a small-molecule binding domain composed of two modules, each able to bind different signal molecules. Malate and succinate were found to bind to the membrane-proximal module, whereas acetate binds to the membrane-distal module. A structural alignment of the two modules revealed that the ligand-binding sites could be superimposed and that amino acids involved in ligand recognition are conserved in both binding sites. Ligand binding to both modules was shown to trigger chemotactic responses. Further analysis showed that McpS-like receptors were found in different classes of proteobacteria, indicating that this mode of response to different carbon sources may be universally distributed. The physiological relevance of the McpS architecture may lie in its capacity to respond with high sensitivity to the preferred carbon sources malate and succinate and, at the same time, mediate lower sensitivity responses to the less preferred but very abundant carbon source acetate. Evidence for chemoreceptors with bimodular ligand-binding regions harboring two signal-binding sites.,Pineda-Molina E, Reyes-Darias JA, Lacal J, Ramos JL, Garcia-Ruiz JM, Gavira JA, Krell T Proc Natl Acad Sci U S A. 2012 Nov 13;109(46):18926-31. doi:, 10.1073/pnas.1201400109. Epub 2012 Oct 29. PMID:23112148[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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