Cotranslational protein integration into the ER membrane is mediated by the binding of nascent chains to translocon proteins

Peter J. McCormick, Yiwei Miao, Yuanlong Shao, Jialing Lin, Arthur E. Johnson

Research output: Contribution to journalArticlepeer-review

90 Citations (Scopus)


During cotranslational protein integration into the ER membrane, each transmembrane (TM) segment moves laterally through the translocon to reach the lipid bilayer. Photocrosslinking studies reveal that a particular surface of each nascent chain TM α helix and signal-anchor sequence always faces Sec61α in the translocon. This nonrandom and TM sequence-dependent positioning reveals that each TM segment makes specific contacts with Sec61α and is retained at a fixed location within the translocon, observations that are best explained by the binding of each TM sequence to a translocon protein(s). Since TM sequence hydrophobicity does not correlate with its rate of release from the translocon, nascent chain movement through the translocon appears to be mediated primarily by protein-protein interactions rather than hydrophobic nascent chain-phospholipid interactions.
Original languageEnglish
Pages (from-to)329-341
Number of pages13
JournalMolecular Cell
Issue number2
Publication statusPublished - 1 Aug 2003

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