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Protein Transport by Purified Yeast Sec Complex and Kar2p Without Membranes

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Science  15 Aug 1997:
Vol. 277, Issue 5328, pp. 938-941
DOI: 10.1126/science.277.5328.938

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Abstract

Posttranslational protein translocation across the endoplasmic reticulum membrane of yeast requires a seven-component transmembrane complex (the Sec complex) in collaboration with the lumenal Kar2 protein (Kar2p). A translocation substrate was initially bound to the cytosolic face of the purified Sec complex in a signal-sequence–dependent but Kar2p- and nucleotide-independent manner. In a subsequent reaction, in which Kar2p interacted with the lumenal face of the Sec complex and hydrolyzed adenosine triphosphate, the substrate moved through a channel formed by the Sec complex and was released at the lumenal end. Movement through the channel occurred in detergent solution in the absence of a lipid bilayer.

  • * To whom correspondence should be addressed. E-mail: rapoport{at}bcmp.med.harvard.edu

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