title: Domain C of human poly(ADP-ribose) polymerase-1 is important for enzyme activity and contains a novel zinc-ribbon motif.
abstract: Poly(ADP-ribose) polymerase-1 (PARP-1) is a multimodular nuclear protein that participates in many fundamental cellular activities. Stimulated by binding to nicked DNA, PARP-1 catalyzes poly(ADP-ribosyl)ation of the acceptor proteins using NAD (+) as a substrate. In this work, NMR methods were used to determine the solution structure of human PARP-1 protein. Domain C was found to contain a zinc-binding motif of three antiparallel beta-strands with four conserved cysteines positioned to coordinate the metal ligand, in addition to a helical region. The zinc-binding motif is structurally reminiscent of the "zinc-ribbon" fold, but with a novel spacing between the conserved cysteines (CX2CX12CX 9C). Domain C alone does not appear to bind to DNA. Interestingly, domain C is essential for PARP-1 activity, since a mixture containing nicked DNA and the PARP-1 ABDEF domains has only basal enzymatic activity, while the addition of domain C to the mixture initiated NAD (+) hydrolysis and the formation of poly(ADP-ribose), as detected by an NMR-based assay and autoradiography. The structural model for domain C in solution provides an important framework for further studies aimed at improving our understanding of how the various domains within the complex PARP-1 enzyme play their respective roles in regulating the enzyme activity when cells are under conditions of genotoxic stress.
authors.affiliation: Division of Medicinal Chemistry, College of Pharmacy, Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712, USA.
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Tao
authors.forename: Peng
authors.initials: P
authors.lastname: Gao
authors.forename: David W
authors.initials: DW
authors.lastname: Hoffman
authors.forename: Hung-Wen
authors.initials: HW
authors.lastname: Liu
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003545:Cysteine / Q000737:chemistry; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011065:Poly(ADP-ribose) Polymerases / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013950:Thymus Gland / Q000378:metabolism; D015032:Zinc / Q000737:chemistry*
chemical_list: D011065:Poly(ADP-ribose) Polymerases; D015032:Zinc; D003545:Cysteine