RING finger, HC subclass, found in midline-2 (MID2) and similar proteins
MID2, also known as midin-2, midline defect 2, RING finger protein 60 (RNF60), or tripartite motif-containing protein 1 (TRIM1), is a probable E3 ubiquitin-protein ligase that is highly related to MID1 that associate with cytoplasmic microtubules along their length and throughout the cell cycle. Like MID1, MID2 associates with the microtubule network and may at least partially compensate for the loss of MID1. Both MID1 and MID2 interacts with Alpha 4, which is a regulatory subunit of PP2-type phosphatases, such as PP2A, and an integral component of the rapamycin-sensitive signaling pathway. MID2 can also substitute for MID1 to control exocytosis of lytic granules in cytotoxic T cells. Loss-of-function mutations in MID2 lead to the human X-linked intellectual disability (XLID). MID2 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 C3HC4-type RING-HC finger, Bbox1 and Bbox2, and a coiled coil region, as well as a COS (carboxy-terminal subgroup one signature) box, a fibronectin type III (FN3) domain, and a B30.2/SPRY (SplA and ryanodine receptor) domain positioned C-terminal to the RBCC domain. MID2 hetero-dimerizes in vitro with its paralog MID1.