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Science. 2016 Jan 1;351(6268):88-91. doi: 10.1126/science.aad4992.

Structure of the Sec61 channel opened by a signal sequence.

Author information

1
MRC Laboratory of Molecular Biology, Medical Research Council, Francis Crick Avenue, Cambridge CB2 0QH, UK.
2
MRC Laboratory of Molecular Biology, Medical Research Council, Francis Crick Avenue, Cambridge CB2 0QH, UK. rhegde@mrc-lmb.cam.ac.uk.

Abstract

Secreted and integral membrane proteins compose up to one-third of the biological proteome. These proteins contain hydrophobic signals that direct their translocation across or insertion into the lipid bilayer by the Sec61 protein-conducting channel. The molecular basis of how hydrophobic signals within a nascent polypeptide trigger channel opening is not understood. Here, we used cryo-electron microscopy to determine the structure of an active Sec61 channel that has been opened by a signal sequence. The signal supplants helix 2 of Sec61α, which triggers a rotation that opens the central pore both axially across the membrane and laterally toward the lipid bilayer. Comparisons with structures of Sec61 in other states suggest a pathway for how hydrophobic signals engage the channel to gain access to the lipid bilayer.

PMID:
26721998
PMCID:
PMC4700591
DOI:
10.1126/science.aad4992
[Indexed for MEDLINE]
Free PMC Article

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