RAZUL (Rpn10 AZUL-binding) domain of 26S proteasome non-ATPase regulatory subunit 4 (PSMD4) and similar proteins
PSMD4 is also called 26S proteasome regulatory subunit RPN10, 26S proteasome regulatory subunit S5A, antisecretory factor 1, AF, ASF, or multiubiquitin chain-binding protein (MCB1). It acts as a ubiquitin receptor subunit through ubiquitin-interacting motifs and selects ubiquitin-conjugates for destruction. It displays a preferred selectivity for longer polyubiquitin chains. PSMD4 is a component of the 26S proteasome, a multiprotein complex involved in the ATP-dependent degradation of ubiquitinated proteins. The proteasome participates in numerous cellular processes, including cell cycle progression, apoptosis, or DNA damage repair. The model corresponds to the C-terminal Rpn10 AZUL-binding domain (RAZUL) of PSMD4, which is responsible for binding the AZUL domain of E6AP/UBE3A. AZUL stands for amino-terminal zinc-binding domain of ubiquitin E3a ligase.