SP-RING finger and SPL-RING finger, variants of RING fingers
This family corresponds to a group of proteins with variants of RING fingers that are characterized by lacking the second, fifth, and sixth Zn2+ ion-coordinating residues compared with the classic C3H2C3-/C3HC4-type RING fingers. They include SP-RING finger found in the Siz/PIAS RING (SP-RING) family of SUMO E3 ligases and SPL-RING finger found in E3 SUMO-protein ligase NSE2. The SP-RING family includes PIAS (protein inhibitor of activated STAT) proteins, Zmiz proteins, and Siz proteins from plants and fungi. The PIAS (protein inhibitor of activated STAT) protein family modulates the activity of several transcription factors and acts as an E3 ubiquitin ligase in the sumoylation pathway. NSE2, also known as MMS21 homolog (MMS21) or non-structural maintenance of chromosomes element 2 homolog (Non-SMC element 2 homolog, NSMCE2), is an autosumoylating small ubiquitin-like modifier (SUMO) ligase required for the response to DNA damage. It regulates sumoylation and nuclear-to-cytoplasmic translocation of skeletal and heart muscle-specific variant of the alpha subunit of nascent polypeptide associated complex (skNAC)-Smyd1 in myogenesis. It is also required for resisting extrinsically induced genotoxic stress.
Structure:4FO9; Homo sapiens E3 Sumo Ligase Pias2 binds one Zn2+ ion through its SP-RING finger.
Structure:4MVT; Homo sapiens Sumo E3 Ligase Pias3 binds one Zn2+ ion through its SP-RING finger.
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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",