RING-CH finger, H2 subclass (C4HC3-type), found in membrane-associated RING-CH3 (MARCH3)
MARCH3, also known as membrane-associated RING finger protein 3, or membrane-associated RING-CH protein III (MARCH-III), or RING finger protein 173 (RNF173), is an E3 ubiquitin-protein ligase that is broadly expressed and is found at relatively high levels in spleen, colon, and lung. It is localized to early endosomes, binds to MARCH2 and syntaxin 6, and is involved in the regulation of vesicular trafficking and fusion of the transport vesicles in endosomes. MARCH3 is the closest homolog of MARCH2 and it is also a functional homolog of K3 and K5 viral ubiquitin E3 ligases related to immune-evasion strategies used by Kaposi's sarcoma-associated herpesvirus (KSHV). Its E2 specificity significantly overlaps that of MARCH2. MARCH3 contains a C4HC3-type RING-CH finger, also known as vRING or RINGv, a variant of C3H2C3-type RING-H2 finger, in the N-terminal cytoplasmic region, two transmembrane domains in the middle region, and a PDZ-binding motif at the C-terminus. The RING-CH finger and PDZ-binding motif are essential for the subcellular localization of MARCH3 and the inhibitory effect on transferrin uptake.
Comment:based on the structure of human MARCH8 with bound Zn2+ ions through its RING-CH finger
Comment:RING-CH finger (C4HC3-type)
Comment:A RING finger typically binds two zinc atoms, with its Cys and/or His side chains in a unique "cross-brace" arrangement.
Comment:The RING fingers found in MARCH proteins have an unusual arrangement of zinc-coordinating residues: The conserved helix complete with tryptophan at the C-terminal end is present but the cysteines and histidines are arranged in the sequence as C4HC3-type, rather than the typical C3H2C3-type in RING-H2 finger.
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