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Publication Abstract from PubMed

The proteasome core particle (CP) is a conserved protease complex that is formed by the stacking of two outer alpha-rings and two inner beta-rings. The alpha-ring is a heteroheptameric ring of subunits alpha1 to alpha7 and acts as a gate that restricts entry of substrate proteins into the catalytic cavity formed by the two abutting beta-rings. The 31-kDa proteasome inhibitor (PI31) was originally identified as a protein that binds to the CP and inhibits CP activity in vitro, but accumulating evidence indicates that PI31 is required for physiological proteasome activity. To clarify the in vivo role of PI31, we examined the Saccharomyces cerevisiae PI31 ortholog Fub1. Fub1 was essential in a situation where the CP assembly chaperone Pba4 was deleted. The lethality of Deltafub1 Deltapba4 was suppressed by deletion of the N terminus of alpha7 (alpha7DeltaN), which led to the partial activation of the CP. However, deletion of the N terminus of alpha3, which activates the CP more efficiently than alpha7DeltaN by gate opening, did not suppress Deltafub1 Deltapba4 lethality. These results suggest that the alpha7 N terminus has a role in CP activation different from that of the alpha3 N terminus and that the role of Fub1 antagonizes a specific function of the alpha7 N terminus.

N-terminal alpha7 deletion of the proteasome 20S core particle substitutes for yeast PI31 function.,Yashiroda H, Toda Y, Otsu S, Takagi K, Mizushima T, Murata S Mol Cell Biol. 2015 Jan;35(1):141-52. doi: 10.1128/MCB.00582-14. Epub 2014 Oct, 20. PMID:25332237^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.