Phosphorylated CheA donates its phosphoryl groups to the CheY response regulator, and the phosphorylated CheY (CheY-P) interacts with the flagellar motor and triggers the clockwise rotation resulting in tumbling. The decreased concentration of an attractant chemical detected by the chemoreceptor LBD promotes CheA autophosphorylation. Chemoreceptor homodimers form mixed trimers-of-dimers, which are packed into a ternary hexagonal array with a histidine kinase CheA and a scaffolding protein CheW. Approximately half of known bacterial species have chemotaxis machinery genes encoded in their genomes, but the molecular mechanism of chemotaxis is best studied in the single model organism Escherichia coli where chemical signals are detected by ligand-binding domains (LBDs) of transmembrane chemoreceptors. This process, called chemotaxis, is vital for finding nutrients, escaping toxins, and establishing relationships with hosts. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist.īacteria utilize flagellar motility to navigate toward or away from spatial gradients of chemical stimuli. L and D.-F.L.), the program Youth Innovation Promotion Association CAS (2014079 to D.-F.L.) and the US National Institutes of Health (R35GM131760 to I.B.Z.). All other relevant data are within the paper and its Supporting Information file.įunding: This work was supported by grants from the National Natural Science Foundation of China (9205110037 to D.-F.L.), National Key R&D Program of China (2019YFA0905500 to S.-J. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: The structure factor and coordinate files have been deposited in the Protein Data Bank under the accession codes number 7WRM. Received: SeptemAccepted: NovemPublished: December 11, 2023Ĭopyright: © 2023 Guo et al. Stock, Rutgers University-Robert Wood Johnson Medical School, UNITED STATES (2023) Attractant and repellent induce opposing changes in the four-helix bundle ligand-binding domain of a bacterial chemoreceptor. We propose a model to illustrate how positive and negative signals might be generated.Ĭitation: Guo L, Wang Y-H, Cui R, Huang Z, Hong Y, Qian J-W, et al. We also observed opposing effects of repellent and attractant binding on the orientation of an alpha helix connecting the sensory domain to the transmembrane helix. We found that malate and citrate affect the oligomerization state of the ligand-binding domain in opposing way. Binding determinants for a repellent and an attractant had only minor differences, and a single amino acid substitution in the binding site inverted the response to malate from a repellent to an attractant. Here, we identified malate as a repellent recognized by the MCP2201 chemoreceptor in a bacterium Comamonas testosteroni and showed that it binds to the same site as an attractant citrate. Mechanisms of sensing attractants are well understood however, molecular aspects of how bacteria sense repellents have not been established. Motile bacteria navigate toward favorable conditions and away from unfavorable environments using chemotaxis.
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