B-box-type 1 zinc finger found in tripartite motif-containing protein 9 (TRIM9) and similar proteins
TRIM9 (the human ortholog of rat Spring), also termed RING finger protein 91 (RNF91), is a brain-specific E3 ubiquitin-protein ligase collaborating with an E2 ubiquitin conjugating enzyme UBCH5b. TRIM9 plays an important role in the regulation of neuronal functions and participates in neurodegenerative disorders through its ligase activity. It interacts with the WD repeat region of beta-transducer repeat-containing protein (beta-TCP) through its N-terminal degron motif depending on the phosphorylation status, and thus negatively regulate nuclear factor-kappaB (NF-kappaB) activation in the NF-kappaB pro-inflammatory signaling pathway. Moreover, TRIM9 acts as a critical catalytic link between Netrin-1 and exocytosis soluble NSF attachment receptor protein (SNARE) machinery in murine cortical neurons. It promotes SNARE-mediated vesicle fusion and axon branching in a Netrin-dependent manner. TRIM9 belongs to the C-I 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, Bbox1 and Bbox2, and a coiled coil region, as well as a COS (carboxyl-terminal subgroup one signature) box, the fibronectin type III domain and the SPRY/B30.2 domain positioned C-terminal to the RBCC domain. The type 1 B-box (Bbox1) zinc finger is characterized by a C6H2 zinc-binding consensus motif.
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