PMID:9618480
| Citation |
Park, H, Saha, SK and Inouye, M (1998) Two-domain reconstitution of a functional protein histidine kinase. Proc. Natl. Acad. Sci. U.S.A. 95:6728-32 |
|---|---|
| Abstract |
In prokaryotes, in the absence of protein serine/threonine/tyrosine kinases, protein histidine kinases play a major role in signal transduction involved in cellular adaptation to various environmental changes and stresses. Histidine kinases phosphorylate their cognate response regulators at a specific aspartic acid residue with ATP in response to particular environmental signals. In this His-Asp phosphorelay signal transduction system, it is still unknown how the histidine kinase exerts its enzymatic function. Here we demonstrate that the cytoplasmic kinase domain of EnvZ, a transmembrane osmosensor of Escherichia coli can be further divided into two distinct functional subdomains: subdomain A [EnvZ(C). (223-289); 67 residues] and subdomain B [EnvZ(C).(290-450); 161 residues]. Subdomain A, with a high helical content, contains the autophosphorylation site, H-243, and forms a stable dimer having the recognition site for OmpR, the cognate response regulator of EnvZ. Subdomain B, an alpha/beta-protein, exists as a monomer. When mixed, the two subdomains reconstitute the kinase function to phosphorylate subdomain A at His-243 in the presence of ATP. Subsequently, the phosphorylated subdomain A is able to transfer its phosphate group to OmpR. The two-domain structure of this histidine kinase provides an insight into the structural arrangement of the enzyme and its transphosphorylation mechanism. |
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| Keywords |
Bacterial Outer Membrane Proteins/chemistry; Bacterial Outer Membrane Proteins/genetics; Bacterial Outer Membrane Proteins/metabolism; Dimerization; Escherichia coli/enzymology; Escherichia coli Proteins; Multienzyme Complexes; Protein Conformation; Protein Kinases/chemistry; Protein Kinases/genetics; Protein Kinases/metabolism; Signal Transduction |
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