FIG. 4.

In vitro activity of the BA2291 histidine sensor kinase. (A) Autophosphorylation and phosphoryl transfer activity assays of BA2291 purified from E. coli were carried out as described in Materials and Methods. Autophosphorylation and phosphoryl transfer activities of purified B. anthracis BA2291 (5 μM) were compared to those observed for B. subtilis proteins KinA (0.2 μM) and Spo0F (2 μM) in the presence of γ-³²P-labeled ATP at 0 and 60 min. The samples were run on 15% SDS-PAGE gels. (B) Schematic representation of the phosphorelay signal transduction system for sporulation initiation (7). Emphasized is the role of BA2291 in inducing sporulation (in the presence of activating signal) or inhibiting sporulation (in the absence of activating signal or in the presence of pXO1-118 and pXO2-61) by removing phosphoryl groups from Spo0F∼P.