RING-CH finger, H2 subclass (C4HC3-type), found in zinc finger SWIM domain-containing protein 2 (ZSWIM2) and similar proteins
ZSWIM2, also known as MEKK1-related protein X (MEX) or ZZ-type zinc finger-containing protein 2, is a testis-specific E3 ubiquitin ligase that promotes death receptor-induced apoptosis through Fas, death receptor (DR) 3, and DR4 signaling. ZSWIM2 is self-ubiquitinated and targeted for degradation through the proteasome pathway. It also acts as an E3 ubiquitin ligase, through the E2, Ub-conjugating enzymes UbcH5a, UbcH5c, or UbcH6. ZSWIM2 contains four putative zinc-binding domains including an N-terminal SWIM (SWI2/SNF2 and MuDR) domain critical for its ubiquitination and two RING fingers separated by a ZZ zinc finger domain, which was required for interaction with UbcH5a and its self-association. This family corresponds to the first RING finger, which is a C4HC3-type RING-CH finger, also known as vRING or RINGv, rather than the canonical C3H2C3-type RING-H2 finger.