Poly(ADP-ribose) polymerase catalyses the covalent attachment of ADP-ribose units from NAD+ to itself and to a limited number of other DNA binding proteins, which decreases their affinity for DNA. Poly(ADP-ribose) polymerase is a regulatory component induced by DNA damage. The carboxyl-terminal region is the most highly conserved region of the protein. Experiments have shown that a carboxyl 40 kDa fragment is still catalytically active .
Poly(ADP-ribose) polymerases (PARP) are a family of enzymes present in eukaryotes, which catalyze the poly(ADP-ribosyl)ation of a limited number of proteins involved in chromatin architecture, DNA repair, or in DNA metabolism, including PARP itself. PARP, also known as poly(ADP-ribose) synthetase and poly(ADP-ribose) transferase, transfers the ADP-ribose moiety from its substrate, nicotinamide adenine dinucleotide (NAD), to carboxylate groups of aspartic and glutamic residues. Whereas some PARPs might function in genome protection, others appear to play different roles in the cell, including telomere replication and cellular transport. PARP-1 is a multifunctional enzyme. The polypeptide has a highly conserved modular organisation consisting of an N-terminal DNA-binding domain, a central regulating segment, and a C-terminal or F region accommodating the catalytic centre. The F region is composed of two parts: a purely alpha-helical N- terminal domain (alpha-hd), and the mixed alpha/beta C-terminal catalytic domain bearing the putative NAD binding site. Although proteins of the PARP family are related through their PARP catalytic domain, they do not resemble each other outside of that region, but rather, they contain unique domains that distinguish them from each other and hint at their discrete functions. Domains with which the PARP catalytic domain is found associated include zinc fingers, SAP, ankyrin, BRCT, Macro, SAM, WWE and UIM domains [PUBMED:8016868, PUBMED:15273990, PUBMED:15561303].
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