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PolD2 (DNA polymerase delta, subunit 2), C-terminal domain PolD2 (DNA polymerase delta, subunit 2) is an auxiliary subunit of the eukaryotic DNA polymerase delta (PolD) complex thought to play a regulatory role and to serve as a scaffold for PolD assembly by interacting simultaneously with all of the other three subunits. PolD2 is catalytically inactive and lacks the active site residues required for phosphoesterase activity in other members of this superfamily. PolD2 is also involved in the recruitment of several proteins regulating DNA metabolism, including p21, PDIP1, PDIP38, PDIP46, and WRN. Human PolD consists of four subunits: p125 (PolD1), p50 (PolD2), p66(PolD3), and p12(PolD4). PolD is one of three major replicases in eukaryotes. PolD also plays an essential role in translesion DNA synthesis, homologous recombination, and DNA repair. Within the PolD complex, PolD2 tightly associates with PolD3. PolD2 belongs to the metallophosphatase (MPP) superfamily. MPPs are functionally diverse, but share a conserved domain with an active site consisting of two metal ions (usually manganese, iron, or zinc) coordinated with octahedral geometry by a cage of histidine, aspartate, and asparagine residues. The MPP superfamily includes: Mre11/SbcD-like exonucleases, Dbr1-like RNA lariat debranching enzymes, YfcE-like phosphodiesterases, purple acid phosphatases (PAPs), YbbF-like UDP-2,3-diacylglucosamine hydrolases, and acid sphingomyelinases (ASMases). The conserved domain is a double beta-sheet sandwich with a di-metal active site made up of residues located at the C-terminal side of the sheets. This domain is thought to allow for productive metal coordination. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",