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Saccharomyces cerevisiae CDC1 and related proteins, metallophosphatase domain Cdc1 (also known as XlCdc1 in Xenopus laevis) is an endoplasmic reticulum-localized transmembrane lipid phosphatase with a metallophosphatase domain facing the ER lumen. In budding yeast, the gene encoding CDC1 is essential while nonlethal mutations cause defects in Golgi inheritance and actin polarization. Cdc1 mutant cells accumulate an unidentified phospholipid, suggesting that Cdc1 is a lipid phosphatase. Cdc1 mutant cells also have highly elevated intracellular calcium levels suggesting a possible role for Cdc1 in calcium regulation. The 5' flanking region of Cdc1 is a regulatory region with conserved binding site motifs for AP1, AP2, Sp1, NF-1 and CREB. DNA polymerase delta consists of at least four subunits - Pol3, Cdc1, Cdc27, and Cdm1. Cdc1 belongs to the metallophosphatase (MPP) superfamily. MPPs are functionally diverse, but all 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.
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