| Description | This entry represents the zinc-ribbon fold of PADR1 domain [ , , , ].Poly(ADP-ribose) polymerase-1 (PARP-1) is a chromatin-associated enzyme involved in multiple cellular processes including DNA repair, cell cycle control, apoptotic signaling, and transcriptional regulation. Stimulated by binding to nicked DNA, PARP-1 catalyzes poly(ADP-ribosyl)ation of the acceptor proteins using NAD as a substrate. PARP-1 has a modular architecture composed of multiple, independently folded domains that can be generally described in three major segments representing the biochemical activities and functional roles of the enzyme: the DNA-binding domain (DBD), the automodification domain which contains a BRCT fold, and the catalytic domain, which consists of the helical (HD) and the ART subdomains. The catalytic domain of PARP-1 is located at the C-terminal end of the protein. The DNA-binding domain is located at the N terminus of PARP-1 and contains two zinc fingers that bind to various DNA structures, a nuclear localization signal, and a caspase-3 cleavage site. The two N-terminal zinc fingers of PARP-1 bind to DNA structures to trigger activation of the C-terminal catalytic domain of PARP-1. The DBD of human PARP-1 contains yet a third zinc-binding domain, referred to as PADR1, located between the N-terminal PARP-type zinc fingers and the central BRCT domain and it is required to mediate interdomain contacts essential for the efficient assembly of PARP-1 domains [ , , , , , , ].The fold of the PADR1 zinc-binding domain consists of an N-terminal helical region, a central zinc ribbon fold, and a C-terminal tail. Three α-helices form a subdomain at the N terminus, with the first helix extending away from the subdomain. The zinc-binding region forms a separate subdomain, making primarily water-mediated contacts with the N-terminal helical subdomain. The zinc-binding subdomain resembles a zinc ribbon fold with four Cys ligands. The spacing between the four Cys residues is strongly conserved among all organisms, following the pattern C-x(2)-C-x(11,12)-C-x(9)-C where C is cysteine and x(n) is the number of amino acids between the Cys residues. The zinc-binding subdomain contains a three-stranded antiparallel β-sheet, with the first pair of zinc ligands located in the loop running over the top of the sheet. The other pair of zinc ligands is centrally located within β-strands, a result of a long (nine-amino acid) insertion between the third and fourth cysteines. An α-helix on the C-terminal tail of the PADR1 zinc-binding domain contributes to the fold of the N-terminal helical region, and the remainder of the C terminus extends away from the N-terminal subdomain [, , , ]. | Name | PADR1, zinc ribbon fold |
| Short Name | PADR1_Zn_ribbon | Type | Domain |
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