Lee C S, Lucet I, Yudkin M D
Microbiology Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom.
J Bacteriol. 2000 Nov;182(21):6250-3. doi: 10.1128/JB.182.21.6250-6253.2000.
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.
由SpoIIAB催化的SpoIIAA磷酸化有助于调控枯草芽孢杆菌的首个芽孢形成特异性σ因子σ(F)。已知磷酸化的稳态速率异常缓慢，且受蛋白激酶SpoIIAB恢复到催化活性状态的限制。本实验室之前的研究表明，在催化磷酸化后，SpoIIAB处于一种不易释放ADP的形式（SpoIIAB*）。我们现在表明，未反应的SpoIIAA的存在大大降低了ADP从SpoIIAB*-ADP复合物中的释放速率，这表明SpoIIAA可以与SpoIIAB*-ADP形成一种长寿命的三元复合物，其中SpoIIAB形式得以稳定。在对SpoIIAA磷酸化的动力学研究中，三元复合物SpoIIAA-SpoIIAB-ADP可以与短寿命复合物SpoIIAA-SpoIIAB-ADP区分开来，后者在没有酶促反应的情况下很容易产生。
