FIG. 4.

Autodephosphorylation rates of wild-type and mutant CheY proteins. CheY proteins were phosphorylated by incubation with purified radiolabelled CheA-P (see Materials and Methods), and aliquots were removed to 2× SDS sample buffer at various time points. The proteins were separated on 15% polyacrylamide gels, and dried gels were analyzed by phosphorimaging. The results are plotted as percent phosphorylated CheY remaining at indicated times. The zero time point represents labelling of CheY after a 10-s incubation with CheA-P. CheY proteins are indicated as follows: wild-type CheY (•), CheYT87S (▪), CheYT87A (□), CheYT87C (○), CheYT87I (×).