FIG 3 .

Time course assays for phosphotransfer activity. Cognate HK and RR pairs identified by the above profiling experiments were assayed in a time course for phosphotransfer activity. Each HK protein (black) was allowed to reach maximal phosphorylation and then mixed with equimolar amounts of cognate NtrC RR protein (red). Samples were collected at 0, 0.25 0.5, 1 and 5 min, resolved by electrophoresis, imaged, and quantified as described in Materials and Methods. The quantified results are presented as pmol of phosphorylated proteins.