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 α-helical domain and a C-terminal core domain (Glu83–Arg162) containing both α-helical and β-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 α-helical domain, whose mutations have been shown previously to produce a high-osmolarity phenotype.
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Research Article|
December 14 2004
Structural characterization of Escherichia coli sensor histidine kinase EnvZ: the periplasmic C-terminal core domain is critical for homodimerization
Ahmad KHORCHID;
Ahmad KHORCHID
*Division of Molecular and Structural Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, 610 University Avenue, Toronto, Ontario, Canada M5G 2M9
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Masayori INOUYE;
Masayori INOUYE
†Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, NJ 08854, U.S.A.
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Mitsuhiko IKURA
Mitsuhiko IKURA
1
*Division of Molecular and Structural Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, 610 University Avenue, Toronto, Ontario, Canada M5G 2M9
1To whom correspondence should be addressed (email mikura@uhnres.utoronto.ca).
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Publisher: Portland Press Ltd
Received:
July 01 2004
Revision Received:
August 11 2004
Accepted:
September 09 2004
Accepted Manuscript online:
September 09 2004
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2005
Biochem J (2005) 385 (1): 255–264.
Article history
Received:
July 01 2004
Revision Received:
August 11 2004
Accepted:
September 09 2004
Accepted Manuscript online:
September 09 2004
Citation
Ahmad KHORCHID, Masayori INOUYE, Mitsuhiko IKURA; Structural characterization of Escherichia coli sensor histidine kinase EnvZ: the periplasmic C-terminal core domain is critical for homodimerization. Biochem J 1 January 2005; 385 (1): 255–264. doi: https://doi.org/10.1042/BJ20041125
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