title: Stabilization of intramolecular triple/single-strand structure by cationic peptides.
abstract: For better comprehension of possible physiological roles of triple-helical DNA structures, it is important to understand if the proteins can stabilize intramolecular triplex (H-DNA). One plausible mode of stabilization is through the neutralization of electrostatic repulsion of negatively charged phosphates in the three DNA strands by positively charged arginine and lysine residues of a bound protein. To gain an insight into interactions between H-DNA and cationic protein domains, we examined the effect of Lys- and Arg-rich oligopeptides on the B-DNA to H-DNA transition. These oligopeptides as well as another type of polycation, spermine, shifted the equilibrium toward H-DNA. These polycations introduced little change in DNA superhelicity, so that an increase in torsional stress was not responsible for facilitated H-DNA formation. Competing influences of polycations and monovalent cations suggest a significant involvement of electrostatic interactions in H-DNA stabilization. The Arg-rich peptides are more effective in H-DNA stabilization than the Lys-rich ones. However, as inferred from experiments on intermolecular complexes, this is not due to a better stabilization of triple helix or destabilization of double helix. It is possible that Arg-rich peptides interact with the unpaired single strand in H-DNA and stabilize its unpaired conformation.
authors.affiliation: Institute of Biosciences and Technology, Texas A&M University, Houston 77030-3303, USA. vpotaman@ibt.tamu.edu
authors.forename: V N
authors.initials: VN
authors.lastname: Potaman
authors.forename: R R
authors.initials: RR
authors.lastname: Sinden
mesh_terms: D001120:Arginine / Q000737:chemistry / Q000378:metabolism; D002412:Cations; D004247:DNA / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D004278:DNA, Superhelical / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006358:Hot Temperature; D008239:Lysine / Q000737:chemistry / Q000378:metabolism; D009690:Nucleic Acid Conformation / Q000187:drug effects; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism; D010957:Plasmids; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology
chemical_list: D002412:Cations; D004278:DNA, Superhelical; D009842:Oligopeptides; C051802:triplex DNA; D004247:DNA; D001120:Arginine; D012964:Sodium; D008239:Lysine