TRIM21

Tripartite motif-containing protein 21 also known as E3 ubiquitin-protein ligase TRIM21 is a protein that in humans is encoded by the TRIM21 gene. Alternatively spliced transcript variants for this gene have been described but the full-length nature of only one has been determined. It is expressed in most human tissues.

Structure

TRIM21 is a member of the tripartite motif (TRIM) family. The TRIM motif includes three zinc-binding domains, a RING finger domain, a B-box type 1 and a B-box type 2 zinc finger, and a coiled coil region.

Function

TRIM21 is an intracellular antibody effector in the intracellular antibody-mediated proteolysis pathway. It binds to immunoglobulin G as well as immunoglobulin M on antibody marked non-enveloped virions which have infected the cell. Either by autoubiquitination or by ubiquitination of a cofactor, it is then responsible for directing the virions to the proteasome. TRIM21 itself is not degraded in the proteasome unlike both the viral capsid and the bound antibody.