B-box-type 2 zinc finger found in muscle-specific RING finger protein 1 (MuRF-1) and similar proteins
MuRF-1, also known as tripartite motif-containing protein 63 (TRIM63), RING finger protein 28 (RNF28), iris RING finger protein, or striated muscle RING zinc finger, is an E3 ubiquitin-protein ligase in ubiquitin-mediated muscle protein turnover. It is predominantly fast (type II) fibre-associated in skeletal muscle and can bind to many myofibrillar proteins, including titin, nebulin, the nebulin-related protein NRAP, troponin-I (TnI), troponin-T (TnT), myosin light chain 2 (MLC-2), myotilin, and T-cap. The early and robust upregulation of MuRF-1 is triggered by disuse, denervation, starvation, sepsis, or steroid administration resulting in skeletal muscle atrophy. It also plays a role in maintaining titin M-line integrity. It associates with the periphery of the M-line lattice and may be involved in the regulation of the titin kinase domain. It also participates in muscle stress response pathways and gene expression. MuRF-1 belongs to the C-II subclass of TRIM (tripartite motif) family of proteins that are defined by their N-terminal RBCC (RING, Bbox, and coiled coil) domains, including three consecutive zinc-binding domains, a RING finger, Bbox2, and a coiled coil region, as well as a COS (carboxyl-terminal subgroup one signature) box, and an acidic residue-rich (AR) domain. It also harbors a MURF family-specific conserved box (MFC) between its RING-HC finger and Bbox domains. The type 2 B-box (Bbox2) zinc finger is characterized by a CHC3H2 zinc-binding consensus motif.
Jiyao W et al.(2023). "The conserved domain database in 2023.",