Protein translocation by the Sec61/SecY channel.
The conserved protein-conducting channel, referred to as the Sec61 channel in eukaryotes or the SecY channel in eubacteria and archaea, translocates proteins across cellular membranes and integrates proteins containing hydrophobic transmembrane segments into lipid bilayers. Structural studies illustrate how the protein-conducting channel accomplishes these tasks. Three different mechanisms, each requiring a different set of channel binding partners, are employed to move polypeptide substrates: The ribosome feeds the polypeptide chain directly into the channel, a ratcheting mechanism is used by the eukaryotic endoplasmic reticulum chaperone BiP, and a pushing mechanism is utilized by the bacterial ATPase SecA. We review these translocation mechanisms, relating biochemical and genetic observations to the structures of the protein-conducting channel and its binding partners.
Osborne
Andrew R
AR
Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA. Andrew_Osborne@hms.harvard.edu
Rapoport
Tom A
TA
van den Berg
Bert
B
D000818:Animals; D018360:Crystallography, X-Ray; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry* / Q000378:metabolism*; D007473:Ion Channels / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008954:Models, Biological; D008958:Models, Molecular; D021381:Protein Transport; D012270:Ribosomes / Q000378:metabolism; D000069816:SEC Translocation Channels; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship
D005656:Fungal Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; C499383:SEC61 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins