This is a zinc finger domain together with a linker region found in RNF125, a small protein (25kD) that contains a RING domain, three zinc fingers (ZnFs) and a ubiquitin interacting motif (UIM). The C2HC ZnF plays an essential role in the interaction of RNF125 with the E2 UbcH5a, which originates from the requirement of the C2HC-ZnF for the structural stability of the RING domain. A mutation at one of the contact residues in the C2HC-ZnF, a highly conserved M112, resulted in the loss of ubiquitin ligase activity. Furthermore, mutations at the Zn2+ chelating cysteine residues, C100 and C103 of this domain resulted in a loss of activity [1].

1: A C2HC zinc finger is essential for the RING-E2 interaction of the ubiquitin ligase RNF125. Bijlmakers MJ, Teixeira JM, Boer R, Mayzel M, Puig-Sarries P, Karlsson G, Coll M, Pons M, Crosas B; Sci Rep. 2016;6:29232. PMID:27411375