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Mol Biol Cell

Title:		Interactions between Sec complex and prepro-alpha-factor during posttranslational protein transport into the endoplasmic reticulum
Author(s):		Plath K; Wilkinson BM; Stirling CJ; Rapoport TA;
Address:		"Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA"
Journal Title:		Mol Biol Cell
Year:		2004
Volume:		20031114
Issue:		1
Page Number:		1 - 10
DOI:		10.1091/mbc.e03-06-0390
ISSN/ISBN:		1059-1524 (Print) 1059-1524 (Linking)
Abstract:		"Posttranslational translocation of prepro-alpha-factor (ppalphaF) across the yeast endoplasmic reticulum membrane begins with the binding of the signal sequence to the Sec complex, a membrane component consisting of the trimeric Sec61p complex and the tetrameric Sec62p/63p complex. We show by photo-cross-linking that the signal sequence is bound directly to a site where it contacts simultaneously Sec61p and Sec62p, suggesting that there is a single signal sequence recognition step. We found no evidence for the simultaneous contact of the signal sequence with two Sec61p molecules. To identify transmembrane segments of Sec61p that line the actual translocation pore, a late translocation intermediate of ppalphaF was generated with photoreactive probes incorporated into the mature portion of the polypeptide. Cross-linking to multiple regions of Sec61p was observed. In contrast to the signal sequence, neighboring positions of the mature portion of ppalphaF had similar interactions with Sec61p. These data suggest that the channel pore is lined by several transmembrane segments, which have no significant affinity for the translocating polypeptide chain"
Keywords:		"Biological Transport Cell Compartmentation Cloning, Molecular Endoplasmic Reticulum Intracellular Membranes/metabolism Mating Factor Membrane Proteins/*metabolism Membrane Transport Proteins/*metabolism Mutation Peptides/metabolism Protein Binding Protein;"
Notes:		"MedlinePlath, Kathrin Wilkinson, Barrie M Stirling, Colin J Rapoport, Tom A eng GM-54238/GM/NIGMS NIH HHS/ Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. 2003/11/18 Mol Biol Cell. 2004 Jan; 15(1):1-10. doi: 10.1091/mbc.e03-06-0390. Epub 2003 Nov 14"