title: Solution structure of the single-strand break repair protein XRCC1 N-terminal domain.
abstract: XRCC1 functions in the repair of single-strand DNA breaks in mammalian cells and forms a repair complex with beta-Pol, ligase III and PARP. Here we describe the NMR solution structure of the XRCC1 N-terminal domain (XRCC1 NTD). The structural core is a beta-sandwich with beta-strands connected by loops, three helices and two short two-stranded beta-sheets at each connection side. We show, for the first time, that the XRCC1 NTD specifically binds single-strand break DNA (gapped and nicked). We also show that the XRCC1 NTD binds a gapped DNA-beta-Pol complex. The DNA binding and beta-Pol binding surfaces were mapped by NMR and found to be well suited for interaction with single-strand gap DNA containing a 90 degrees bend, and for simultaneously making contacts with the palm-thumb of beta-Pol in a ternary complex. The findings suggest a mechanism for preferential binding of the XRCC1 NTD to flexible single-strand break DNA.
authors.affiliation: Department of Biochemistry, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, Connecticut 06032, USA.
authors.forename: A
authors.initials: A
authors.lastname: Marintchev
authors.forename: M A
authors.initials: MA
authors.lastname: Mullen
authors.forename: M W
authors.initials: MW
authors.lastname: Maciejewski
authors.forename: B
authors.initials: B
authors.lastname: Pan
authors.forename: M R
authors.initials: MR
authors.lastname: Gryk
authors.forename: G P
authors.initials: GP
authors.lastname: Mullen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage / Q000235:genetics*; D019951:DNA Polymerase beta / Q000378:metabolism*; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D019143:Evolution, Molecular; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D018583:Pliability; D011485:Protein Binding; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D012996:Solutions; D013816:Thermodynamics; D000076105:X-ray Repair Cross Complementing Protein 1
chemical_list: D004268:DNA-Binding Proteins; D012996:Solutions; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; D018698:Glutamic Acid; D004247:DNA; D019951:DNA Polymerase beta