Mao Chunfeng, Hardy Simon J S, Randall Linda L
Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, USA.
J Bacteriol. 2009 Feb;191(3):978-84. doi: 10.1128/JB.01321-08. Epub 2008 Oct 31.
SecA is the ATPase that provides energy for translocation of precursor polypeptides through the SecYEG translocon in Escherichia coli during protein export. We showed previously that when SecA receives the precursor from SecB, the ternary complex is fully active only when two protomers of SecA are bound. Here we used variants of SecA and of SecB that populate complexes containing two protomers of SecA to different degrees to examine both the hydrolysis of ATP and the translocation of polypeptides. We conclude that the low activity of the complexes with only one protomer is the result of a low efficiency of coupling between ATP hydrolysis and translocation.
SecA是一种ATP酶，在蛋白质输出过程中，它为大肠杆菌中前体多肽通过SecYEG转运体的转运提供能量。我们之前表明，当SecA从SecB接收前体时，只有当两个SecA原体结合时，三元复合物才具有完全活性。在这里，我们使用了SecA和SecB的变体，它们以不同程度形成包含两个SecA原体的复合物，以研究ATP的水解和多肽的转运。我们得出结论，只有一个原体的复合物活性较低是ATP水解与转运之间偶联效率较低的结果。
