A protein complex required for signal-sequence-specific sorting and translocation.

B Wiedmann; H Sakai; T A Davis; M Wiedmann

doi:10.1038/370434a0

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A protein complex required for signal-sequence-specific sorting and translocation.

B Wiedmann·H Sakai·T A Davis·M Wiedmann

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Abstract

We have purified a nascent-polypeptide-associated complex (NAC) which prevents short ribosome-associated nascent polypeptides from inappropriate interactions with proteins in the cytosol. NAC binds nascent-polypeptide domains emerging from ribosomes unless a signal peptide is fully exposed. Depletion of cytosolic proteins (including NAC) from ribosomes carrying nascent polypeptides allows the signal recognition particle (SRP) to crosslink to polypeptides irrespective of whether or not they contain signal peptides. In the absence of cytosol, proteins lacking signal peptides can be mistranslocated into the endoplasmic reticulum in vitro, albeit with low efficiency. Readdition of NAC restores the specificity of SRP and fidelity of translocation.

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Amino Acid Sequence Animals Biological Transport Cattle Cross-Linking Reagents Cytosol Endoplasmic Reticulum Humans Molecular Sequence Data Peptides Protein Binding Protein Biosynthesis Protein Processing, Post-Translational Protein Sorting Signals Proteins Ribosomes Signal Recognition Particle Journal Article

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B Wiedmann, H Sakai, T A Davis, M Wiedmann. 1994-08-11. A protein complex required for signal-sequence-specific sorting and translocation.. https://doi.org/10.1038/370434a0

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