The inner membrane histidine kinase EnvZ senses osmolality via helix-coil transitions in the cytoplasm

Loo Chien Wang, Leslie K. Morgan, Pahan Godakumbura, Linda Kenney, Ganesh S. Anand

Research output: Contribution to journalArticle

69 Scopus citations

Abstract

Two-component systems mediate bacterial signal transduction, employing a membrane sensor kinase and a cytoplasmic response regulator (RR). Environmental sensing is typically coupled to gene regulation. Understanding how input stimuli activate kinase autophosphorylation remains obscure. The EnvZ/OmpR system regulates expression of outer membrane proteins in response to osmotic stress. To identify EnvZ conformational changes associated with osmosensing, we used HDXMS to probe the effects of osmolytes (NaCl, sucrose) on the cytoplasmic domain of EnvZ (EnvZ c). Increasing osmolality decreased deuterium exchange localized to the four-helix bundle containing the autophosphorylation site (His 243). EnvZ c exists as an ensemble of multiple conformations and osmolytes favoured increased helicity. High osmolality increased autophosphorylation of His 243, suggesting that these two events are linked. In-vivo analysis showed that the cytoplasmic domain of EnvZ was sufficient for osmosensing, transmembrane domains were not required. Our results challenge existing claims of robustness in EnvZ/OmpR and support a model where osmolytes promote intrahelical H-bonding enhancing helix stabilization, increasing autophosphorylation and downstream signalling. The model provides a conserved mechanism for signalling proteins that respond to diverse physical and mechanical stimuli.

Original languageEnglish (US)
Pages (from-to)2648-2659
Number of pages12
JournalEMBO Journal
Volume31
Issue number11
DOIs
StatePublished - May 30 2012
Externally publishedYes

Keywords

  • amide hydrogen deuterium exchange mass spectrometry
  • histidine kinase
  • osmosensing
  • robustness
  • two-component signal transduction

ASJC Scopus subject areas

  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Neuroscience(all)

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