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

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    90 Citations (Scopus)

    Abstract

    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
    Volume12
    Issue number2
    DOIs
    Publication statusPublished - 1 Aug 2003

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