Conformational Transitions that Enable Histidine Kinase Autophosphorylation and Receptor Array Integration.

摘要: During bacterial chemotaxis, transmembrane chemoreceptor arrays regulate autophosphorylation of the dimeric histidine kinase CheA. The five domains CheA (P1-P5) each play a specific role in coupling receptor stimulation to activity. Biochemical and X-ray scattering studies thermostable from Thermotoga maritima determine that His-containing substrate domain (P1) is sequestered by interactions depend upon P1 adjacent subunit. Non-hydrolyzable ATP analogs (but not or ADP) release protein core (domains P3P4P5) increase its mobility. Detachment both removal one within dimer increases net substantially at physiological temperature (55°C). However, nearly all activity lost without dimerization (P3). linker length between P3 dictates intersubunit (trans) versus intrasubunit (cis) autophosphorylation, with trans reaction requiring minimum 47 residues. A new crystal structure most active dimerization-plus-kinase unit (P3P4) reveals directing tether connecting P2-P1 ATP-binding (P4) domain. orientation P4 relative P3P4 supports planar conformation required membrane array models, it suggests lid may be poised interact receptors proteins. Collectively, these data suggest are restrained off-state as result cross-subunit interactions. Perturbations nucleotide-binding pocket mobility access His P4-bound ATP.