FIG. 5.

Kinetic fits to k_obs versus [CheY]. Estimates of the k_obs value were obtained from phosphotransfer data from P∼CheA_FL (A) or P∼CheA_ΔP2 (B) to CheY in the presence (closed symbols) or absence (open symbols) of the CheZ_C15 peptide. The data corresponding to phosphotransfer from P∼CheA_FL to CheY in the absence of the CheZ_C15 peptide are fit to a rectangular hyperbola to define a second-order rate constant, k_phos; the remaining data are fit linearly to define first-order rates (k_phos/K_S). Error bars denote standard errors of replicates.