期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：13
页码：5111-5116
DOI：10.1073/pnas.0809592106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The motor protein SecA drives the transport of polypeptides through the ubiquitous protein channel SecYEG. Changes in protein-nucleotide binding energy during the hydrolytic cycle of SecA must be harnessed to drive large conformational changes resulting in channel opening and vectorial substrate polypeptide transport. Here, we elucidate the ATP hydrolysis cycle of SecA from Escherichia coli by transient and steady-state methods. The basal ATPase activity of SecA is very slow with the release of ADP being some 600-fold slower than hydrolysis. Upon binding to SecYEG the release of ADP is stimulated but remains rate-limiting. ADP release is fastest in the fully coupled system when a substrate protein is being translocated; in this case hydrolysis and ADP release occur at approximately the same rate. The data imply that ADP dissociation from SecA is accompanied by a structural rearrangement that is strongly coupled to the protein interface and protein translocation through SecYEG.
