title: NMR structures of a nonapeptide from DNA binding domain of human polymerase-alpha determined by iterative complete-relaxation-matrix approach.
abstract: Nuclear magnetic resonance structures of a nonapeptide, ERFKCPCPT, selected from the DNA binding domain of human polymerase-alpha, were determined by complete relaxation matrix analysis of transverse NOE data. The structures exhibit a type III turn with residues KCPC, and the remaining residues exhibit non-ordered structures. The turn was confirmed by alpha, N (i,i+3) connectivity, a low temperature coefficient of NH chemical shift (-3.1 x 10(-3)) of the fourth residue, 3J(NHalpha) coupling constants, and characteristic CD peaks at 228 and 200 nm. Furthermore, phi and psi dihedral angles for the i + 1, and i + 2 residues of the turn are found to be -80 and -41 and -60 and -40 degrees. The first proline residue is trans- while the second exists in both cis- and trans- configurations, with trans- being more than 80% populated. The trans-configuration was established from C5alpha-P6alpha correlation and phi and psi angles of the proline. The five-membered proline ring is in DOWN puckered (C-beta-exo/C-gamma-endo) conformation. The structure of the peptide reveals that the two cysteine thiols are approximately 5 A(o) apart and appropriately positioned to covalently bind cis-diamminedichloroplatinum(II), a widely used anti-cancer drug.
authors.affiliation: Department of Chemistry, Kent State University, OH 44242, USA. rbose@platinum.kent.edu
authors.forename: R N
authors.initials: RN
authors.lastname: Bose
authors.forename: D
authors.initials: D
authors.lastname: Li
authors.forename: W W
authors.initials: WW
authors.lastname: Yang
authors.forename: S
authors.initials: S
authors.lastname: Basu
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D004256:DNA Polymerase I / Q000737:chemistry*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding
chemical_list: D010455:Peptides; D004247:DNA; D004256:DNA Polymerase I