Fate of the SpoIIAB*-ADP liberated after SpoIIAB phosphorylates SpoIIAA of Bacillus subtilis.
Phosphorylation of SpoIIAA catalyzed by SpoIIAB helps to regulate the first sporulation-specific sigma factor, sigma(F), of Bacillus subtilis. The steady-state rate of phosphorylation is known to be exceptionally slow and to be limited by the return of the protein kinase, SpoIIAB, to a catalytically active state. Previous work from this laboratory has suggested that, after catalyzing the phosphorylation, SpoIIAB is in a form (SpoIIAB*) that does not readily release ADP. We now show that the rate of release of ADP from the SpoIIAB*-ADP complex was much diminished by the presence of unreacted SpoIIAA, suggesting that SpoIIAA can form a long-lived ternary complex with SpoIIAB*-ADP in which the SpoIIAB* form is stabilized. In kinetic studies of the phosphorylation of SpoIIAA, the ternary complex SpoIIAA-SpoIIAB*-ADP could be distinguished from the short-lived complex SpoIIAA-SpoIIAB-ADP, which can be readily produced in the absence of an enzymatic reaction.
Lee
C S
CS
Microbiology Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom.
Lucet
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I
Yudkin
M D
MD
D000244:Adenosine Diphosphate / Q000378:metabolism; D001412:Bacillus subtilis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D007700:Kinetics; D010766:Phosphorylation; D012808:Sigma Factor; D014157:Transcription Factors
D001426:Bacterial Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C092468:spoIIR protein, Bacillus subtilis; C030069:spore-specific proteins, Bacillus; D000244:Adenosine Diphosphate