Electron microscopic visualization of asymmetric precursor translocation intermediates:SecA functions as a dimer  

作　　者：TAI Phang C 

机构地区：[1]Department of Biology,Georgia State University

出　　处：《Science China(Life Sciences)》2010年第9期1049-1056,共8页中国科学（生命科学英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 30830028);the National Basic Research program of China (Grant No. 2010CD833706/2010CB912400) (S.F.S.);the National Institutes of Health (Grant No. GM34766 to PCT)

摘　　要：SecA,the ATPase of Sec translocase,mediates the post-translational translocation of preprotein through the protein-conduct-ing channel SecYEG in the bacterial inner membrane.Here we report the structures of Escherichia coli Sec intermediates during preprotein translocation as visualized by electron microscopy to probe the oligomeric states of SecA during this process.We found that the translocase holoenzyme is symmetrically assembled by SecA and SecYEG on proteoliposomes,whereas the translocation intermediate 31 (I31) becomes asymmetric because of the presence of preprotein.Moreover,SecA is a dimer in these two translocation complexes.This work also shows surface topological changes in the components of translocation intermediates by immunogold labeling.The channel entry for preprotein translocation was found at the center of the I31 structures.Our results indicate that the presence of preprotein introduces asymmetry into translocation intermediates,while SecA remains dimeric during the translocation process.SecA,the ATPase of Sec translocase,mediates the post-translational translocation of preprotein through the protein-conduct-ing channel SecYEG in the bacterial inner membrane.Here we report the structures of Escherichia coli Sec intermediates during preprotein translocation as visualized by electron microscopy to probe the oligomeric states of SecA during this process.We found that the translocase holoenzyme is symmetrically assembled by SecA and SecYEG on proteoliposomes,whereas the translocation intermediate 31 (I31) becomes asymmetric because of the presence of preprotein.Moreover,SecA is a dimer in these two translocation complexes.This work also shows surface topological changes in the components of translocation intermediates by immunogold labeling.The channel entry for preprotein translocation was found at the center of the I31 structures.Our results indicate that the presence of preprotein introduces asymmetry into translocation intermediates,while SecA remains dimeric during the translocation process.

关 键 词：SECA SECYEG ELECTRON microscopy single particle analysis 

分 类 号：Q936[生物学—微生物学]