A chemoreceptor conformational equilibrium controlled by signaling inputs

• 成果类型: Article
• 署名作者: Hoffman, Mikaila C.; Li, Mingshan; Hazelbauer, Gerald L.; Schlau-Cohen, Gabriela S.
• 署名单位: Massachusetts Institute of Technology (MIT); University of Missouri System; University of Missouri Columbia
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12197
• DOI: 10.1073/pnas.2505872122
• 发表日期: 2025-07-15
• 关键词: alternating-laser excitation; escherichia-coli; aspartate receptor; bacterial chemoreceptor; cytoplasmic domain; structural determinants; sensory adaptation; helix rotation; chemotaxis; mechanism

摘要

In chemotaxis, motile bacteria recognize external molecules and move toward favorable ling, control a histidine kinase, and undergo posttranslational adaptational modifications. Chemoreceptors are thought to function by switching between two signaling states: kinase- off, favored by ligand occupancy, and kinase- on, favored by adaptational modification. Many structural and biochemical features of the two states have been identified, but little is known about the equilibrium between them and the response of that equilibrium tored helical separations in the Escherichia coli aspartate chemoreceptor Tar for the two pairs of helices that form the cytoplasmic four- helix coiled coil bundle. Rather than the commonly assumed switch between two conformations in response to signaling inputs, we identified two separations in each helical pair that were present under all conditions but with variation in relative occupancy. Ligand occupancy and adaptational modification were found to differentially impact the conformational equilibria, rather than reversing symmetrical packing in the four- helix bundle into rhomboid packing, whereas adaptational modification determined which helical pair was central in the rhombus. Thus, the structural consequence of ligand binding was not stabilization of a specific helical conformation but instead the collective geometry of all helices in the bundle. Such changes in helical geometry may play a role in conformational signaling by other transmembrane receptors.