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Transport of proteins in and out of the endoplasmic reticulum
Author(s) -
Rapoport Tom A
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a207-c
Subject(s) - endoplasmic reticulum associated protein degradation , sec61 , endoplasmic reticulum , microbiology and biotechnology , transport protein , membrane protein , cytosol , stim1 , translocon , biology , chemistry , biochemistry , membrane , unfolded protein response , enzyme
Many proteins are transported during their biosynthesis across or are integrated into the endoplasmic reticulum (ER) membrane or the bacterial plasma membrane. Transport occurs through a protein‐conducting channel, formed from a conserved heterotrimeric membrane protein complex (Sec61/SecYcomplex). The channel associates with different partners in different translocation pathways. The crystal structure of an archaeal SecY complex suggests mechanisms for how the membrane barrier for small molecules can be maintained during translocation, how the signal sequence is recognized, and how trans‐membrane segments of nascent membrane proteins exit into lipid. In eukarotes, there is a much less understood translocation pathway in the reverse direction, called ERAD (for ER‐associated degradation), by which misfolded ER proteins are transported back into the cytosol where they are poly‐ubiquitinated and degraded by the proteasome. Different, but convergent, ERAD pathways are used for proteins with misfolded domains in the lumen, membrane, or cytosol (called ERAD‐L, ‐M, and –C, respectively). The recent identification of most, if not all, components of the ERAD pathways paves the way for a mechanistic understanding of retro‐translocation.