The UBA domain of Ubc1 (Ube2K) Facilitates the Assembly of K48/K63-Branched Ubiquitin Chains

ABSTRACT: The assembly of a specific polymeric ubiquitin (Ub) chain on a target protein is a key event in the regulation of numerous cellular processes. Yet, the mechanisms that govern the selective synthesis of particular polyubiquitin signals remain enigmatic. The ubiquitin-conjugating (E2) enzymes Ubc1 in yeast and Ube2K in mammals exclusively generate polyubiquitin linked through lysine 48 (K48). Uniquely among E2 enzymes, Ubc1 and Ube2K harbor a Ub binding UBA domain with unknown function. We found that this UBA domain preferentially interacts with Ub chains linked through lysine 63 (K63). Based on structural modeling, in vitro ubiquitination experiments and NMR studies, we propose that the UBA domain aligns Ubc1 with K63-linked polyubiquitin and facilitates the selective assembly of K48/K63-branched Ub molecules. Genetic experiments link the activity of the UBA domain and hence the formation of this unusual Ub chain topology to the maintenance of cellular proteostasis.

INSTRUMENT(S): Orbitrap Exploris 480, Q Exactive HF

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

SUBMITTER: Henrik Zauber  

LAB HEAD: Matthias Selbach

PROVIDER: PXD022621 | Pride | 2021-03-02

REPOSITORIES: Pride