RING-CH finger, H2 subclass (C4HC3-type), found in membrane-associated RING-CH1 (MARCH1)
MARCH1, also known as membrane-associated RING finger protein 1, membrane-associated RING-CH protein I (MARCH-I), or RING finger protein 171 (RNF171), is a membrane-anchored E3 ubiquitin ligase that is mainly expressed in cells of the immune system. It regulates antigen presentation and T-cell costimulatory functions of dendritic cells by down-regulating the cell surface expression of major histocompatibility complex class II (MHCII) and CD86 molecules. It mediates ubiquitination of MHCII and CD86 in dendritic cells (DCs). This ubiquitination induces MHCII and CD86 endocytosis, lysosomal transport, and degradation. MARCH1 also plays a regulatory role in T cell activation during immune responses, as well as in splenic DC homeostasis. Moreover, MARCH1 may regulate its own expression through dimerization and autoubiquitination. MARCH1 contains an N-terminal cytoplasmic C4HC3-type RING-CH finger, also known as vRING or RINGv, a variant of C3H2C3-type RING-H2 finger and two transmembrane domains.
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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