The protein translocation channel binds proteasomes to the endoplasmic reticulum membrane

EMBO J. 2005 Jul 6;24(13):2284-93. doi: 10.1038/sj.emboj.7600731. Epub 2005 Jun 23.

Abstract

Misfolded secretory proteins are transported across the endoplasmic reticulum (ER) membrane into the cytosol for degradation by proteasomes. A large fraction of proteasomes in a cell is associated with the ER membrane. We show here that binding of proteasomes to ER membranes is salt sensitive, ATP dependent, and mediated by the 19S regulatory particle. The base of the 19S particle, which contains six AAA-ATPases, binds to microsomal membranes with high affinity, whereas the 19S lid complex binds weakly. We demonstrate that ribosomes and proteasomes compete for binding to the ER membrane and have similar affinities for their receptor. Ribosomes bind to the protein conducting channel formed by the Sec61 complex in the ER membrane. We co-precipitated subunits of the Sec61 complex with ER-associated proteasome 19S particles, and found that proteoliposomes containing only the Sec61 complex retained proteasome binding activity. Collectively, our data suggest that the Sec61 channel is a principal proteasome receptor in the ER membrane.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / metabolism
  • Animals
  • Dogs
  • Endoplasmic Reticulum / metabolism*
  • Intracellular Membranes / metabolism
  • Membrane Proteins / metabolism*
  • Membrane Transport Proteins
  • Microsomes / metabolism
  • Proteasome Endopeptidase Complex / metabolism*
  • Protein Binding
  • Protein Folding
  • Protein Transport
  • Ribosomes / metabolism
  • SEC Translocation Channels
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins

Substances

  • Membrane Proteins
  • Membrane Transport Proteins
  • SEC Translocation Channels
  • SEC61 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Proteasome Endopeptidase Complex
  • Adenosine Triphosphatases