RING finger, HC subclass, found in E3 ubiquitin-protein ligase XIAP, baculoviral IAP repeat-containing protein 8 (BIRC8) and similar proteins
XIAP, also known as baculoviral IAP repeat-containing protein 4 (BIRC4), IAP-like protein (ILP), inhibitor of apoptosis protein 3 (IAP-3), or X-linked inhibitor of apoptosis protein (X-linked IAP), is a potent suppressor of apoptosis that directly inhibits specific members of the caspase family of cysteine proteases, including caspase-3, -7, and -9. It promotes proteasomal degradation of caspase-3 and enhances its anti-apoptotic effect in Fas-induced cell death. The ubiquitin-protein ligase (E3) activity of XIAP also exhibits in the ubiquitination of second mitochondria-derived activator of caspases (Smac). The mitochondrial proteins, Smac/DIABLO and Omi/HtrA2, can inhibit the antiapoptotic activity of XIAP. XIAP has also been implicated in several intracellular signaling cascades involved in the cellular response to stress, such as the c-Jun N-terminal kinase (JNK), the nuclear factor-kappaB (NF-kappaB), and the transforming growth factor-beta (TGF-beta) pathways. Moreover, XIAP can regulate copper homeostasis by interacting with MURR1. BIRC8, also known as inhibitor of apoptosis-like protein 2, IAP-like protein 2, ILP-2, or testis-specific inhibitor of apoptosis, is a tissue-specific homolog of E3 ubiquitin-protein ligase XIAP. It has been implicated in the control of apoptosis in the testis by direct inhibition of caspase 9. Both XIAP and BIRC8 contain three N-terminal baculoviral IAP repeat (BIR) domains, a ubiquitin-association (UBA) domain and a C3HC4-type RING-HC finger at the carboxyl terminus.
Comment:C3HC4-type RING-HC finger consensus motif: C-X2-C-X(9-39)-C-X(1-3)-H-X(2-3)-C-X2-C-X(4-48)-C-X2-C, where X is any amino acid and the number of X residues varies in different fingers
Comment:A RING finger typically binds two zinc atoms, with its Cys and/or His side chains in a unique "cross-brace" arrangement.
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