Structural characterization of Escherichia coli sensor histidine kinase EnvZ: the periplasmic C-terminal core domain is critical for homodimerization

Biochem J. 2005 Jan 1;385(Pt 1):255-64. doi: 10.1042/BJ20041125.

Abstract

Escherichia coli EnvZ is a membrane sensor histidine kinase that plays a pivotal role in cell adaptation to changes in extracellular osmolarity. Although the cytoplasmic histidine kinase domain of EnvZ has been extensively studied, both biochemically and structurally, little is known about the structure of its periplasmic domain, which has been implicated in the mechanism underlying its osmosensing function. In the present study, we report the biochemical and biophysical characterization of the periplasmic region of EnvZ (Ala38-Arg162). This region was found to form a dimer in solution, and to consist of two well-defined domains: an N-terminal a-helical domain and a C-terminal core domain (Glu83-Arg162) containing both a-helical and b-sheet secondary structures. Our pull-down assays and analytical ultracentrifugation analysis revealed that dimerization of the periplasmic region is highly sensitive to the presence of CHAPS, but relatively insensitive to salt concentration, thus suggesting the significance of hydrophobic interactions between the homodimeric subunits. Periplasmic homodimerization is mediated predominantly by the C-terminal core domain, while a regulatory function may be attributed mainly to the N-terminal a-helical domain, whose mutations have been shown previously to produce a high-osmolarity phenotype.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacterial Outer Membrane Proteins / chemistry*
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / isolation & purification
  • Bacterial Outer Membrane Proteins / metabolism*
  • Conserved Sequence
  • Dimerization
  • Escherichia coli / enzymology*
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / isolation & purification
  • Escherichia coli Proteins / metabolism*
  • Histidine Kinase
  • Leucine / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Multienzyme Complexes / chemistry*
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / isolation & purification
  • Multienzyme Complexes / metabolism*
  • Periplasm / enzymology*
  • Protein Kinases / chemistry*
  • Protein Kinases / genetics
  • Protein Kinases / isolation & purification
  • Protein Kinases / metabolism*
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary

Substances

  • Bacterial Outer Membrane Proteins
  • Escherichia coli Proteins
  • Multienzyme Complexes
  • Protein Kinases
  • Histidine Kinase
  • envZ protein, E coli
  • Leucine