Hsm3 is a yeast Proteasome chaperone of the 19S regulatory particle and related proteins
This group contains proteins related to the Hsm3 protein (Yeast Proteasome Interacting Protein) of Saccharomyces cerevisiae. S. cerevisiae Hsm3 is a chaperone of regulatory particles involved in proteasome assembly. The 26S Proteasome is a large, 2.5 MDa complex comprised of at least 33 subunits, and relies on chaperones to facilitate correct assembly. The proteasome contains a cylindrical 20S core particle and 1-2 19S regulatory particles, comprised of AAA-ATPase and non-ATPase subunits. The proteasome acts in ubiquitin-dependent proteolysis. The 19S RP targets and opens the the ubiquitin-tagged substrate and releases ubiquitin. Hsm3 acts as a 19S chaperone, binding to the C-terminal domain of Rpt1 (the 6 ATPase subunits of the 19 S regulatory particle(s). Hsm3 has a C-shape composed of 11 HEAT repeats. Mutations in the Hsm3-Rpt interface disrupt formation of the 26 S Proteasome complex.
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