RING, which is the abbreviation of "Really Interesting New Gene", represents a zinc finger type structural domain with a C3HC4 amino acid motif which binds two zinc cations (1). It is observed that the cysteine and histidine residues are conserved and help maintain the structure. During the ubiquitination catalyzed by RING E3s, the ubiquitin is directly transferred from E2 to the substrate. Although the RING ligases might be single chains or complexes, the RING domains present the E3 ligase activity by binding E2s and activate E2s to discharge its ubiquitin cargo. Furthermore, RING domain proteins usually function as oligomers. Since the organization of RING E3 ligases, RING domain proteins are involved in a variety of biological functions (2).

1. http://pfam.xfam.org/family/PF00097

2. Deshaies, R.J. and Joazeiro, C.A. (2009). RING domain E3 ubiquitin ligases. Annu. Rev. Biochem., 78, 399-434. PMID: 19489725