Role of HAMP domains in chemotaxis signaling by bacterial chemoreceptors

Cezar M. Khursigara, Xiongwu Wu, Peijun Zhang, Jonathan Lefman, Sriram Subramaniam

Research output: Contribution to journalArticle

Abstract

Bacterial chemoreceptors undergo conformational changes in response to variations in the concentration of extracellular ligands. These changes in chemoreceptor structure initiate a series of signaling events that ultimately result in regulation of rotation of the flagellar motor. Here we have used cryo-electron tomography combined with 3D averaging to determine the in situ structure of chemoreceptor assemblies in Escherichia coli cells that have been engineered to overproduce the serine chemoreceptor Tsr. We demonstrate that chemoreceptors are organized as trimers of receptor dimers and display two distinct conformations that differ principally in arrangement of the HAMP domains within each trimer. Ligand binding and methylation alter the distribution of chemoreceptors between the two conformations, with serine binding favoring the "expanded" conformation and chemoreceptor methylation favoring the "compact" conformation. The distinct positions of chemoreceptor HAMP domains within the context of a trimeric unit are thus likely to represent important aspects of chemoreceptor structural changes relevant to chemotaxis signaling. Based on these results, we propose that the compact and expanded conformations represent the "kinase-on" and "kinase-off" states of chemoreceptor trimers, respectively.

Original languageEnglish (US)
Pages (from-to)16555-16560
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume105
Issue number43
DOIs
Publication statusPublished - Oct 28 2008
Externally publishedYes

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Keywords

  • Cryo-electron tomography
  • Molecular architecture
  • Signal transduction

ASJC Scopus subject areas

  • General

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