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 language | English |
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Pages (from-to) | 329-341 |
Number of pages | 13 |
Journal | Molecular Cell |
Volume | 12 |
Issue number | 2 |
DOIs | |
Publication status | Published - 1 Aug 2003 |