SP-RING finger found in Arabidopsis thaliana E3 SUMO-protein ligase SIZ1 (AtSIZ1) and similar proteins
SIZ1-mediated conjugation of SUMO1 and SUMO2 to other intracellular proteins is essential in Arabidopsis. AtSIZ1 negatively regulates abscisic acid (ABA) signaling through the sumoylation of bZIP transcripton factor ABI5. It also mediates sumoylation of bromodomain GTE proteins. Moreover, AtSIZ1 regulates flowering by controlling a salicylic acid-mediated floral promotion pathway and through affecting on FLOWERING LOCUS C (FLC) chromatin structure. It also plays a role in drought stress response likely through the regulation of gene expression. Members of this subfamily contain an N-terminal SAP (scaffold attachment factor A/B (SAF-A/B), acinus and PIAS) box, a plant homeodomain (PHD) finger, and a specific RING finger known as Siz/PIAS (protein inhibitor of activated signal transducer and activator of transcription) RING (SP-RING) finger. The SP-RING finger is a variant of RING finger, which lacks the second, fifth, and sixth zinc-binding residues of the consensus C3H2C3-/C3HC4-type RING fingers. It binds a single Zn ion, instead of two ions bound by typical RING fingers.
Comment:based on the structures of human Sumo ligases Pias2 and Pias3 with bound Zn2+ ion through their SP-RING fingers
Comment:The SP-RING finger is a variant of RING finger; it binds a single Zn ion and lacks the second, fifth, and sixth zinc-binding residues of the consensus C3H2C3-/C3HC4-type RING fingers.
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