BACTERIAL CHEMOTAXIS SIGNALING COMPLEXES - FORMATION OF A CHEA/CHEW COMPLEX ENHANCES AUTOPHOSPHORYLATION AND AFFINITY FOR CHEY

We have demonstrated that a complex of the proteins CheA (CheA(L) and CheA(S)) and CheW can be isolated and constitutes a functional unit that responds to the signaling state of the chemoreceptors. The autophosphorylation rate of CheA(L) is much greater when CheA(L) and CheA(S) are complexed with CheW. Moreover, the presence of mutant chemoreceptors that cause cells to tumble increases this rate. At wild-type levels of expression, the isolated CheA(L)/CheA(S)/CheW complex accounts for about 10% of the total number of CheA(L), CheA(S), and CheW molecules and exists in a 1:1:1 stoichiometry. This complex is also required for CheA(L)/CheA(S) and CheW binding to the phosphorylation substrate, CheY. A separate interaction between CheY and another chemotaxis component, CheZ, was also detected. The CheY-CheZ interaction does not require participation of the CheA(L)/CheA(S)/CheW complex.