Phosphorylation kinetics of wild-type CheY by PAM. Reactions were
performed in the absence of peptide (○), the presence of 1
mM FliM peptide (□), the presence of 1 mM CheZ peptide
(⋄), the presence of 15 μM CheA-P2 (▵), or the presence
of 1 mM CheZ205VE peptide (×). Measurements were done with a
stopped-flow instrument, and constant ionic strength was maintained.
Observed first-order rate constants (kobs)
were determined from individual phosphorylation time courses at the
indicated phosphodonor concentrations. For clarity,
kobs values obtained in the absence of
peptide (○) and in the presence of CheA-P2 (▵)
are replotted in Inset with a different
y-axis scale.