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.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenosine Triphosphate / metabolism
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Biological Transport
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Cross-Linking Reagents
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Cytosol / metabolism
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Detergents
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Digitonin
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Endoplasmic Reticulum / metabolism
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Fungal Proteins / metabolism*
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HSP70 Heat-Shock Proteins / metabolism*
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Heat-Shock Proteins*
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Lipid Bilayers
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Liposomes / metabolism
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Membrane Proteins / metabolism*
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Membrane Transport Proteins*
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Protein Precursors / metabolism*
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Protein Sorting Signals / metabolism
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Proteolipids / metabolism
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RNA, Transfer / metabolism
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SEC Translocation Channels
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Saccharomyces cerevisiae Proteins*
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Solubility
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Succinimides
Substances
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Cross-Linking Reagents
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Detergents
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Fungal Proteins
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HSP70 Heat-Shock Proteins
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Heat-Shock Proteins
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KAR2 protein, yeast
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Lipid Bilayers
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Liposomes
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MF(ALPHA)1 protein, S cerevisiae
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Membrane Proteins
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Membrane Transport Proteins
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Protein Precursors
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Protein Sorting Signals
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Proteolipids
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SEC Translocation Channels
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SEC62 protein, S cerevisiae
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SEC63 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Succinimides
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proteoliposomes
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Adenosine Triphosphate
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RNA, Transfer
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Digitonin
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disuccinimidyl suberate