title: The proteasome-associated protein Ecm29 inhibits proteasomal ATPase activity and in vivo protein degradation by the proteasome.
abstract: Several proteasome-associated proteins regulate degradation by the 26 S proteasome using the ubiquitin chains that mark most substrates for degradation. The proteasome-associated protein Ecm29, however, has no ubiquitin-binding or modifying activity, and its direct effect on substrate degradation is unclear. Here, we show that Ecm29 acts as a proteasome inhibitor. Besides inhibiting the proteolytic cleavage of peptide substrates in vitro, it inhibits the degradation of ubiquitin-dependent and -independent substrates in vivo. Binding of Ecm29 to the proteasome induces a closed conformation of the substrate entry channel of the core particle. Furthermore, Ecm29 inhibits proteasomal ATPase activity, suggesting that the mechanism of inhibition and gate regulation by Ecm29 is through regulation of the proteasomal ATPases. Consistent with this, we identified through chemical cross-linking that Ecm29 binds to, or in close proximity to, the proteasomal ATPase subunit Rpt5. Additionally, we show that Ecm29 preferentially associates with both mutant and nucleotide depleted proteasomes. We propose that the inhibitory ability of Ecm29 is important for its function as a proteasome quality control factor by ensuring that aberrant proteasomes recognized by Ecm29 are inactive.
authors.affiliation: From the Molecular, Cellular, and Developmental Biology Program, Division of Biology, and.
authors.forename: Alina
authors.initials: A
authors.lastname: De La Mota-Peynado
authors.forename: Stella Yu-Chien
authors.initials: SY
authors.lastname: Lee
authors.forename: Brianne Marie
authors.initials: BM
authors.lastname: Pierce
authors.forename: Prashant
authors.initials: P
authors.lastname: Wani
authors.forename: Chingakham Ranjit
authors.initials: CR
authors.lastname: Singh
authors.forename: Jeroen
authors.initials: J
authors.lastname: Roelofs
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D009154:Mutation; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D059748:Proteolysis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D057149:Ubiquitinated Proteins / Q000378:metabolism
chemical_list: C551357:Ecm29 protein, S cerevisiae; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D057149:Ubiquitinated Proteins; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D000251:Adenosine Triphosphatases; C541345:RPT5 protein, S cerevisiae
keywords: ATP-dependent Protease; ATPases; Molecular Chaperone; Protease Inhibitor; Proteasome; Protein Degradation; Ubiquitin-dependent Protease