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Protein Domain : Poly(ADP-ribose) polymerase, catalytic domain

Primary Identifier  IPR012317 Type  Domain
Short Name  Poly(ADP-ribose)pol_cat_dom
description  Poly(ADP-ribose) polymerases (PARP) are a family of enzymespresent in eukaryotes, which catalyze the poly(ADP-ribosyl)ation of a limitednumber of proteins involved in chromatin architecture, DNA repair, or in DNAmetabolism, including PARP itself. PARP, also known as poly(ADP-ribose)synthetase and poly(ADP-ribose) transferase, transfers the ADP-ribose moietyfrom its substrate, nicotinamide adenine dinucleotide (NAD), to carboxylategroups of aspartic and glutamic residues. Whereas some PARPs might function ingenome protection, others appear to play different roles in the cell,including telomere replication and cellular transport. PARP-1 is amultifunctional enzyme. The polypeptide has a highly conserved modularorganisation consisting of an N-terminal DNA-binding domain, a centralregulating segment, and a C-terminal or F region accommodating the catalyticcentre. The F region is composed of two parts: a purely α-helical N-terminal domain (alpha-hd), and the mixed alpha/beta C-terminal catalyticdomain bearing the putative NAD binding site. Although proteins of the PARPfamily are related through their PARP catalytic domain, they do not resembleeach other outside of that region, but rather, they contain unique domainsthat distinguish them from each other and hint at their discrete functions.Domains with which the PARP catalytic domain is found associated includezinc fingers, SAP, ankyrin, BRCT, Macro, SAM, WWE and UIM domains [, , ].The alpha-hd domain is about 130 amino acids in length and consists of an up-up-down-up-down-down motif of helices. It isthought to relay the activation signal issued on binding to damaged DNA [, ].The PARP catalytic domain is about 230 residues in length. Its core consists of a five-stranded antiparallel β-sheet andfour-stranded mixed β-sheet. The two sheets are consecutive and areconnected via a single pair of hydrogen bonds between two strands that run atan angle of 90 degrees. These central β-sheets are surrounded by five α-helices, three 3(10)-helices, and by a three- and a two-stranded β-sheet ina 37-residue excursion between two central β-strands [, ]. The activesite, known as the 'PARP signature' is formed by a block of 50 amino acids that is strictly conserved among the vertebrates andhighly conserved among all species. The 'PARP signature' is characteristic ofall PARP protein family members. It is formed by a segment of conserved aminoacid residues formed by a β-sheet, an α-helix, a 3(10)-helix, a β-sheet, and an α-helix [].

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84 Protein Domain Regions