The Sec62/63 translocon facilitates membrane insertion and C-terminal translocation of multi-spanning membrane proteins

• Majority of membrane proteins are co-translationally translocated. The Sec62/Sec63 complex which mediates post-translational translocation of a subset of primarily secretory proteins into the endoplasmic reticulum (ER),  therefore has been thought uninvolved in targeting and translocation of membrane proteins. By systematic analysis of single and multi-spanning membrane proteins with broad sequence context; varying hydrophobicity, flanking charged residues and orientation of transmembrane (TM) segments, in a set of Sec62 mutant yeast strains, we show that mutations in the N-terminal cytosolic domain of Sec62 impair interaction with Sec63 and lead to defects in membrane insertion and the C-terminal translocation of membrane proteins. These results reveal an unappreciated function of the Sec62/Sec63 translocon as a general membrane chaperone that regulates topogenesis of membrane proteins in the eukaryotic cell.

Subject headings

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Keyword

endoplasmic reticulum

co-translational translocation

Sec61

topology

yeast

Publication and Content Type

vet (subject category)

ovr (subject category)