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- Title
X-ray structure of a protein-conducting channel.
- Authors
Van den Berg, Bert; Clemons, William M, Jr; Collinson, Ian; Modis, Yorgo; Hartmann, Enno; Harrison, Stephen C; Rapoport, Tom A
- Abstract
A conserved heterotrimeric membrane protein complex, the Sec61 or SecY complex, forms a protein-conducting channel, allowing polypeptides to be transferred across or integrated into membranes. We report the crystal structure of the complex from Methanococcus jannaschii at a resolution of 3.2 A. The structure suggests that one copy of the heterotrimer serves as a functional translocation channel. The alpha-subunit has two linked halves, transmembrane segments 1-5 and 6-10, clamped together by the gamma-subunit. A cytoplasmic funnel leading into the channel is plugged by a short helix. Plug displacement can open the channel into an 'hourglass' with a ring of hydrophobic residues at its constriction. This ring may form a seal around the translocating polypeptide, hindering the permeation of other molecules. The structure also suggests mechanisms for signal-sequence recognition and for the lateral exit of transmembrane segments of nascent membrane proteins into lipid, and indicates binding sites for partners that provide the driving force for translocation.
- Publication
Nature, 2004, Vol 427, Issue 6969, p36
- ISSN
1476-4687
- Publication type
Journal Article
- DOI
10.1038/nature02218