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A monomeric histidine kinase derived from EnvZ, an Escherichia coli osmosensor
Author(s) -
Qin Ling,
Dutta Rinku,
Kurokawa Hirofumi,
Ikura Mitsuhiko,
Inouye Masayori
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.01837.x
Subject(s) - histidine kinase , autophosphorylation , histidine , biology , biochemistry , kinase , protein kinase domain , escherichia coli , function (biology) , phosphatase , phosphorylation , enzyme , protein kinase a , microbiology and biotechnology , mutant , gene
Histidine kinases function as dimers. The kinase domain of the osmosensing histidine kinase EnvZ of Escherichia coli consists of two domains: domain A (67 residues) responsible for histidine phosphotransfer and dimerization, and domain B (161 residues) responsible for the catalytic and ATP‐binding function. The individual structures of these two domains have been recently solved by NMR spectroscopy. Here, we demonstrate that an enzymatically functional monomeric histidine kinase can be constructed by fusing in tandem two domains A and one domain B to produce a single polypeptide (A–A–B). We show that this protein, EnvZc[AAB], is soluble and exists as a stable monomer. The autophosphorylation and OmpR kinase activities of the monomeric EnvZc[AAB] are similar to that of the wild‐type EnvZ, while OmpR‐binding and phosphatase functions are reduced. V8 protease digestion and mutational analyses indicate that His‐243 of only the amino proximal domain A is phosphorylated. Based on these results, molecular models are proposed for the structures of EnvZc[AAB] and the kinase domain of EnvZ. The present results demonstrate for the first time the construction of a functional, monomeric histidine kinase, further structural studies of which may provide important insights into the structure–function relationships of histidine kinases.