PROSITE documentation PDOC51292

Zinc finger RING-CH-type profile

The RING finger is a well characterized zinc finger which coordinates two zinc atoms in a cross-braced manner (see <PDOC00449>). According to the pattern of cysteines and histidines three different subfamilies of RING finger can be defined. The classical RING finger (RING-HC) has a histidine at the fourth coordinating position and a cysteine at the fifth. In the RING-H2 variant, both the fourth and fifth positions are occupied by histidines. The RING-CH, which is very similar to the classical RING finger, differs from both of these variants in that it has a cys residue in the fourth position and a His in the fifth. Another difference between the RING-CH and the common RING variants is a somewhat longer peptide segment between the fourth and fifth zinc-coordinating residues. The RING-CH zinc finger has thus the same arrangement of cysteine and histidine (C4HC3) as the PHD zinc finger (see <PDOC50016>) but it contains features (spacing between the cysteines and the histidine) characteristic of the genuine RING-finger (C3HC4) [1,2]. The RING-CH-type is an E3 ligase mainly found in proteins associated to membranes [3,4].

The solution structure of the RING-CH-type zinc finger of the herpesvirus Mir1 protein has shown that it is an outlying relative of the cellular RING finger domain family, with its polypeptide backbone much more closely resembling that of RING domains than PHD domains (see <PDB:1VYX>) [5]. The only real difference between the classic and variant RING domains, other than the alteration of zinc ligands, is the loss of the small β-sheet found in RING domains and the replacement of one strand of this sheet with a single turn of helix.

Some proteins that contains a RING-CH-type zinc finger are listed below:

• Yeast Doa10/SSM4. An E3 ligase essential for the endoplasmic reticulum associated degradation (ERAD), an ubiquitin-proteasome system responsible for the degradation of membrane and lumenal proteins of the endoplasmic reticulum.
• Mammalian membrane-associated RING-CH 1 to 9 (MARCH1 to 9) proteins.
• Herpesvirus modulator of immune recognition 1. An E3 ubiquitin-protein ligase which promotes ubiquitination and subsequent degradation of host MHC-I and CD1D molecules, presumably to prevent lysis of infected cells by cytotoxic T-lymphocytes.

The profile we developed covers the entire RING-CH-type zinc finger.