Journal of Bacteriology, November 2000, p. 6250-6253, Vol. 182, No. 21
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Microbiology Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
Received 15 June 2000/Accepted 10 August 2000
Phosphorylation of SpoIIAA catalyzed by SpoIIAB helps to regulate
the first sporulation-specific
factor,
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.
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