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：2003
卷号：100
期号：8
页码：4604-4609
DOI：10.1073/pnas.0730860100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The translocation of proteins across cellular membranes is a key mechanistic problem for every cell. The preprotein translocon at the chloroplast outer envelope is responsible for precursor protein recognition and translocation across the outer envelope. We have reconstituted the translocation process into proteoliposomes from single subunits or by using the purified translocon. Precursor proteins are recognized by the Toc34 receptor in an initial GTP-dependent process. Translocation across the plane of the membrane then occurs through the Toc75 channel in a GTP-dependent process. Correspondingly, GTP hydrolysis of Toc proteoliposomes is 100-fold enhanced in the presence of preprotein. Complete translocation is demonstrated by processing of the precursor form to the mature form by the stromal processing peptidase and by protease resistance of the imported protein. Molecular chaperones are not involved in this translocation event. We show that Toc159 acts as a GTP-driven motor in a sewing-machine-like mechanism.
