Blm10 binds to pre-activated proteasome core particles with open gate conformation.

Blm10 is bound to the yeast proteasome core particle, a crucial protease of eukaryotic cells [corrected]. Two gates, at both ends of the CP, control the access of protein substrates to the catalytic cavity of the CP. Normally, substrate access is auto-inhibited by a closed gate conformation unless regulatory complexes ...
are bound to the CP and translocate protein substrates in an ATP-dependent manner. Here, we provide evidence that Blm10 recognizes pre-activated open gate CPs, which are assumed to exist in an equilibrium with inactive closed gate CP. Consequently, single-capped Blm10-CP shows peptide hydrolysis activity. Under conditions of disturbed CP assembly, as well as in open gate mutants, pre-activated CP or constitutively active CP, respectively, prevail. Then, Blm10 sequesters disordered and open gate CP by forming double-capped Blm10(2)-CP in which peptide hydrolysis activity is repressed. We conclude that Blm10 distinguishes between gate conformations and regulates the activation of CP.
Mesh Terms:
Enzyme Activation, Enzyme Stability, Models, Biological, Molecular Chaperones, Mutation, Proteasome Endopeptidase Complex, Protein Binding, Protein Conformation, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
EMBO Rep.
Date: Dec. 01, 2008
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