human CTD phosphatase subunit 1 (CTDP1/FCP1) and related proteins; belongs to the haloacid dehalogenase-like superfamily
Human CTDP1/FCP1 is a protein phosphatase which dephosphorylates the phosphorylated C terminus (CTD) of RNA polymerase II. CTD phosphorylation is a key mechanism of regulation of gene expression in eukaryotes. CTDP1/FCP1 may have other roles in in transcription regulation independent of its phosphatase activity. This family also includes human translocase of inner mitochondrial membrane 50 (TIMM50), CTD small phosphatase like (CTDSPL) and CTD small phosphatase like 2 (CTDSPL2), Saccharomyces cerevisiae (nuclear envelope morphology protein 1) Nem1p, and Xenopus Dullard. Yeast Nem1p in complex with Spo7p dephosphorylates the nuclear membrane-associated phosphatidic acid phosphatase, Smp2p, which may be part of a signaling cascade playing a role in nuclear membrane biogenesis. Xenopus Dullard is a potential regulator of neural tube development. Members of this family belong to the haloacid dehalogenase-like (HAD) hydrolases, a large superfamily of diverse enzymes that catalyze carbon or phosphoryl group transfer reactions on a range of substrates, using an active site aspartate in nucleophilic catalysis. Members of this superfamily include 2-L-haloalkanoic acid dehalogenase, azetidine hydrolase, phosphonoacetaldehyde hydrolase, phosphoserine phosphatase, phosphomannomutase, P-type ATPases and many others. HAD hydrolases are found in all three kingdoms of life, and most genomes are predicted to contain multiple HAD-like proteins. Members possess a highly conserved alpha/beta core domain, and many also possess a small cap domain, the fold and function of which is variable. HAD hydrolases are sometimes referred to as belonging to the DDDD superfamily of phosphohydrolases.
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