BRcat domain found in RING finger protein 144B (RNF144B)
RNF144B, also called PIR2, IBR domain-containing protein 2 (IBRDC2), or p53-inducible RING finger protein (p53RFP), is a transmembrane (TM) domain-containing RBR E3 ubiquitin-protein ligase that induces p53-dependent but caspase-independent apoptosis. It interacts with E2 ubiquitin-conjugating enzymes UbcH7 and UbcH8, but not with UbcH5. It is involved in ubiquitination and degradation of p21, a p53 downstream protein promoting growth arrest and antagonizing apoptosis, suggesting a role in switching a cell from p53-mediated growth arrest to apoptosis. Moreover, RNF144B regulates the levels of Bax, a pro-apoptotic protein from the Bcl-2 family, and protects cells from unprompted Bax activation and cell death. It also regulates epithelial homeostasis by mediating degradation of p21WAF1 and p63. RNF144B contains an RBR domain followed by a potential single-TM domain. The RBR domain was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been changed to RING1-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase functions to facilitate the ubiquitination reaction. This model corresponds to the BRcat domain of RNF144B that adopts the same fold as the Rcat domain while lacking the catalytic cysteine residue and ubiquitination activity.
Jiyao W et al.(2023). "The conserved domain database in 2023.",