Active Site Interference and Asymmetric Activation in the Chemotaxis Protein Histidine Kinase CheA*

The histidine protein kinase CheA is a multidomain protein that mediates stimulus-response coupling in bacterial chemotaxis. We have previously shown that the purified protein exhibits an equilibrium between inactive monomer and active dimer (Surette, M., Levit, M., Liu, Y., Lukat, G., Ninfa, E., Ninfa, A., and Stock, J. (1996) J. Biol. Chem. 271, 939-945). We report here a study of the kinetics of phosphorylation of the isolated …