The signaling pathway in histidine kinase and the response regulator complex revealed by X-ray crystallography and solution 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 A 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 A 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 (Kd=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-Sim (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.
Yamada
Seiji
S
Biometal Science Laboratory, RIKEN SPring-8 Center, Harima Institute, Hyogo 679-5148, Japan.
Akiyama
Shuji
S
Sugimoto
Hiroshi
H
Kumita
Hideyuki
H
Ito
Kazuki
K
Fujisawa
Tetsuro
T
Nakamura
Hiro
H
Shiro
Yoshitsugu
Y
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D000071677:Histidine Kinase; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D011487:Protein Conformation; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012542:Scattering, Radiation; D016415:Sequence Alignment; D015398:Signal Transduction; D020124:Thermotoga maritima / Q000737:chemistry* / Q000201:enzymology
D001426:Bacterial Proteins; D046912:Multiprotein Complexes; D011494:Protein Kinases; D000071677:Histidine Kinase