Structural highlights
Function[SECY_METJA] The central subunit of the protein translocation channel SecYEG. Consists of two halves formed by TMs 1-5 and 6-10. These two domains form a lateral gate at the front which open onto the bilayer between TMs 2 and 7, and are clamped together by SecE at the back. The channel is closed by both a pore ring composed of hydrophobic SecY resides and a short helix (helix 2A) on the extracellular side of the membrane which forms a plug. The plug probably moves laterally to allow the channel to open. The ring and the pore may move independently. [SECE_METJA] Essential subunit of the protein translocation channel SecYEG. Clamps together the 2 halves of SecY. May contact the channel plug during translocation. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedA 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. X-ray structure of a protein-conducting channel.,Van den Berg B, Clemons WM Jr, Collinson I, Modis Y, Hartmann E, Harrison SC, Rapoport TA Nature. 2004 Jan 1;427(6969):36-44. Epub 2003 Dec 3. PMID:14661030[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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