期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 362, 期 1, 页码 123-139出版社
ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2006.07.012
关键词
histidine kinase; response regulator; crystal structure; small-angle X-ray scattering
The structure of a histidine kinase (ThkA) complexed with a response regulator (TrrA) in the two-component regulatory system from hyperthermophile Thermotoga maritima was determined by a combination of X-ray crystallography at a resolution of 4.2 angstrom and small-angle X-ray scattering (SAXS). The boundary of the three component domains (PAS-sensor, dimerization and catalytic domains) of ThkA and the bound TrrA molecule were unambiguously assigned in the electron density map at 4.2 angstrom resolution. ThkA forms a dimer with crystallographic 2-fold symmetry and two monomeric TrrAs bind to the ThkA dimer. SAXS experiments also confirmed this association state in solution and specific binding between ThkA and TrrA (K-d=8.2x10(-11) M-2). The association interface between ThkA and TrrA contains the phosphotransfer His residue in the ThkA, indicative of an efficient receipt of the phosphoryl group. One Per-Arnt-Sirn (PAS) domain does not interact with the other PAS domain, but with the catalytic domain of the same polypeptide chain and with one TrrA molecule. Observed inter-domain and inter-molecular interactions reveal a definite pathway of signal transduction in the kinase/regulator complex. In addition, we propose a responsible role of TrrA for the feedback regulation of sensing and/or kinase activities of ThkA. (c) 2006 Elsevier Ltd. All rights reserved.
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