title: Structural specificity of peptides in Z-DNA formation and energetics of the peptide-induced B-Z transition of poly(dG-m5dC).
abstract: The effects of oligopeptide binding in the conformation of double-stranded poly(dG-m5dC) have been examined by circular dichroism spectroscopy. Conversion from the right-handed B-form to the left-handed Z-form occurs very efficiently in the presence of peptides having amino acid sequences of the (Lys-X)n-Lys type, where X is a non-bulky amino acid residue such as Gly, Ala and Lys. The ability to induce the B-Z transition increases rapidly with increasing repeat number n, and the peptides with n = 2-3 readily convert the B-form DNA to the Z-form at a peptide/nucleotide molar ratio of 0.06 to 0.08 (one peptide per 13 to 17 nucleotides). The peptide-induced B-Z transition of poly(dG-m5dC) duplexes takes place even at a physiological salt concentration (150 mM NaCl). The activation energy and van't Hoff enthalpy of the B-Z conversion have been determined to be 124 (+/- 7) and 138 (+/- 12) kJ/mol, respectively, for the (Lys-Gly)2-Lys-induced transition. The van 't Hoff enthalpy of the peptide-induced B-Z transition is particularly small compared to those of the transitions caused by other inducers. The large enthalpic contribution to the Z-DNA formation indicates that the peptide binds preferentially to the Z-arranged DNA phosphate groups and stabilizes the Z-stretch significantly. It is pointed out that some DNA-binding proteins have amino acid sequences that favor Z-DNA.
authors.affiliation: Pharmaceutical Institute, Tohoku University, Sendai, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Takeuchi
authors.forename: N
authors.initials: N
authors.lastname: Hanamura
authors.forename: I
authors.initials: I
authors.lastname: Harada
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008745:Methylation; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000737:chemistry* / Q000378:metabolism; D012965:Sodium Chloride; D013816:Thermodynamics
chemical_list: D004268:DNA-Binding Proteins; D011089:Polydeoxyribonucleotides; D012965:Sodium Chloride; C029988:poly(dG-m(5)dC).poly(dG-m(5)dC); D004247:DNA