X-ray structure of a protein-conducting channel

Bert Van Den Berg, William M. Clemons, Ian Collinson, Yorgo Modis, Enno Hartmann, Stephen C. Harrison, Tom A. Rapoport*

*Corresponding author for this work
787 Citations (Scopus)


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 Å. The structure suggests that one copy of the heterotrimer serves as a functional translocation channel. The α-subunit has two linked halves, transmembrane segments 1-5 and 6-10, clamped together by the γ-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.

Original languageEnglish
Issue number6969
Pages (from-to)36-44
Number of pages9
Publication statusPublished - 01.01.2004


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