Ring Finger Protein 181 (RNF181)

RNF181 binds the integrin alpha-IIb (ITGA2B)/beta-3 (ITGB3) complex and has E3 ubiquitin ligase activity. The 153-amino acid protein contains a RING finger domain. RT-PCR analysis detected highest levels of expression in liver and heart, moderate levels in placenta, lung, liver, kidney, pancreas, and lower levels in brain and skeletal muscle. Western blot analysis detected RNF181 protein in human platelets as a 36-kD dimer and an 18-kD monomer.

In vitro ubiquitination assay demonstrated that RNF181 acts as a ubiquitin E3 ligase and is self-ubiquitinated as part of the enzymatic reaction. The authors showed that protein ubiquitination in platelets occurred in response to platelet activation by intracellular Ca(2+).