Essential role for ubiquitin-ubiquitin-conjugating enzyme interaction in ubiquitin discharge from Cdc34 to substrate.

ABSTRACT: During ubiquitin conjugation, the thioester bond that links "donor" ubiquitin to ubiquitin-conjugating enzyme (E2) undergoes nucleophilic attack by the ɛ-amino group of an acceptor lysine, resulting in formation of an isopeptide bond. Models of ubiquitination have envisioned the donor ubiquitin to be a passive participant in this process. However, we show here that the I44A mutation in ubiquitin profoundly inhibits its ability to serve as a donor for ubiquitin chain initiation or elongation, but can be rescued by computationally predicted compensatory mutations in the E2 Cdc34. The donor defect of ubiquitin-I44A can be partially suppressed either by using a low pKa amine (hydroxylamine) as the acceptor or by performing reactions at higher pH, suggesting that the discharge defect arises in

SUBMITTER: Saha A 

PROVIDER: S-EPMC3091889 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature