The source of high signal cooperativity in bacterial chemosensory arrays

Germán E. Piñas, Vered Frank, Ady Vaknin, John S. Parkinson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

The Escherichia coli chemosensory system consists of large arrays of transmembrane chemoreceptors associated with a dedicated histidine kinase, CheA, and a linker protein, CheW, that couples CheA activity to receptor control. The kinase activity responses to receptor ligand occupancy changes can be highly cooperative, reflecting allosteric coupling of multiple CheA and receptor molecules. Recent structural and functional studies have led to a working model in which receptor core complexes, the minimal units of signaling, are linked into hexagonal arrays through a unique interface 2 interaction between CheW and the P5 domain of CheA. To test this array model, we constructed and characterized CheA and CheW mutants with amino acid replacements at key interface 2 residues. The mutant proteins proved defective in interface 2-specific in vivo cross-linking assays, and formed signaling complexes that were dispersed around the cell membrane rather than clustered at the cell poles as in wild type chemosensory arrays. Interface 2 mutants down-regulated CheA activity in response to attractant stimuli in vivo, but with much less cooperativity than the wild type. Moreover, mutant cells containing fluorophore-tagged receptors exhibited greater basal anisotropy that changed rapidly in response to attractant stimuli, consistent with facile changes in loosely packed receptors. We conclude that interface 2 lesions disrupt important network connections between core complexes, preventing receptors from operating in large, allosteric teams. This work confirms the critical role of interface 2 in organizing the chemosensory array, in directing the clustered array to the cell poles, and in producing its highly cooperative signaling properties.

Original languageAmerican English
Pages (from-to)3335-3340
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume113
Issue number12
DOIs
StatePublished - 22 Mar 2016

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. We thank Dr. Claudia Studdert (Instituto de Agrobiotecnología del Litoral, Santa Fe, Argentina) for sharing plasmids containing CheW interface 2 mutations and for helpful comments on the manuscript. This work was supported by US Public Health Service Research Grant GM19559 from the National Institute of General Medical Sciences (to J.S.P.), by the Israeli Foundation of Sciences and Humanities (to A.V.), and US-Israel Binational Science Foundation Research Grant 2011463 (to A.V. and J.S.P.). The Protein-DNA Core Facility at the University of Utah receives support from National Cancer Institute Grant CA42014 to the Huntsman Cancer Institute.

Keywords

  • Chemoreceptors
  • Chemotaxis
  • Kinase activity
  • Stimulus response

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