RING finger, HC subclass, found in Saccharomyces cerevisiae histone E3 ligase 2 (HEL2) and similar proteins
HEL2 is an E3 ubiquitin-protein ligase that interacts with the E2 ubiquitin-conjugating enzyme UBC4 and histones H3 and H4. It plays an important role in regulating histone protein levels and also likely to contribute to the maintenance of genomic stability in the budding yeast. HEL2 can be phosphorylated by the DNA damage checkpoint kinase and histone protein regulator Rad53. This subfamily also includes Schizosaccharomyces pombe histone E3 ligase 1 (HEL1), also known as DNA-break-localizing protein 4 (dbl4), and Dictyostelium discoideum Ariadne-like ubiquitin ligase (RbrA). RbrA may act as an E3 ubiquitin-protein ligase that appears to be required for normal cell-type proportioning and cell sorting during multicellular development, and is also necessary for spore cell viability. Members of this subfamily contain an RBR domain that was previously known as RING-BetweenRING-RING domain or TRIAD [two RING fingers and a DRIL (double RING finger linked)] domain. Based on current understanding of the structural biology of RBR ligases, the nomenclature of RBR has been corrected as RING-BRcat (benign-catalytic)-Rcat (required-for-catalysis) recently. The RBR (RING1-BRcat-Rcat) domain uses an auto-inhibitory mechanism to modulate ubiquitination activity, as well as a hybrid mechanism that combines aspects from both RING and HECT E3 ligase function to facilitate the ubiquitination reaction. This model corresponds to the RING domain, a C3HC4-type RING-HC finger required for RBR-mediated ubiquitination.
Comment:C3HC4-type RING-HC finger consensus motif: C-X2-C-X(9-39)-C-X(1-3)-H-X(2-3)-C-X2-C-X(4-48)-C-X2-C, where X is any amino acid and the number of X residues varies in different fingers
Comment:A RING finger typically binds two zinc atoms, with its Cys and/or His side chains in a unique "cross-brace" arrangement.
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