FIGURE 3.

M. tuberculosis STPK interactions are substrate-specific. Inter-kinase phosphorylation occurs in a substrate-specific pattern and is not due to differences in enzyme activity. PknB, PknD, and PknH, three STPKs with differing activity, were incubated with the PknB and PknD Asp-to-Asn mutant kinases. Time points taken at 30, 60, and 120 min and 24 h after reaction initiation display the same relative inter-kinase phosphorylation patterns (lower band) when Western-blotted with a phosphothreonine antibody. Active STPK autophosphorylation was similar at each time point (upper bands). Coomassie-stained gels demonstrate equal substrate protein concentrations in all reactions.