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Annu Rev Cell Dev Biol. 2017 Oct 6;33:369-390. doi: 10.1146/annurev-cellbio-100616-060439. Epub 2017 May 31.

Structural and Mechanistic Insights into Protein Translocation.

Author information

1
Department of Cell Biology, Howard Hughes Medical Institute and Harvard Medical School, Boston, Massachusetts 02115; email: tom_rapoport@hms.harvard.edu , Long_Li@hms.harvard.edu.
2
The Rockefeller University and Howard Hughes Medical Institute, New York, NY 10065; email: epark@rockefeller.edu.

Abstract

Many proteins are translocated across the endoplasmic reticulum (ER) membrane in eukaryotes or the plasma membrane in prokaryotes. These proteins use hydrophobic signal sequences or transmembrane (TM) segments to trigger their translocation through the protein-conducting Sec61/SecY channel. Substrates are first directed to the channel by cytosolic targeting factors, which use hydrophobic pockets to bind diverse signal and TM sequences. Subsequently, these hydrophobic sequences insert into the channel, docking into a groove on the outside of the lateral gate of the channel, where they also interact with lipids. Structural data and biochemical experiments have elucidated how channel partners, the ribosome in cotranslational translocation, and the eukaryotic ER chaperone BiP or the prokaryotic cytosolic SecA ATPase in posttranslational translocation move polypeptides unidirectionally across the membrane. Structures of auxiliary components of the bacterial translocon, YidC and SecD/F, provide additional insight. Taken together, these recent advances result in mechanistic models of protein translocation.

KEYWORDS:

Sec proteins; endoplasmic reticulum; membrane barrier; membrane protein; ribosome

[Indexed for MEDLINE]

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