title: Reversible pH Switch of Two-Quartet G-Quadruplexes Formed by Human Telomere.
abstract: A four-repeat human telomere DNA sequence without the 3'-end guanine, d[TAGGG(TTAGGG)2 TTAGG] (htel1-ΔG23) has been found to adopt two distinct two G-quartet antiparallel basket-type G-quadruplexes, TD and KDH(+) in presence of KCl. NMR, CD, and UV spectroscopy have demonstrated that topology of KDH(+) form is distinctive with unique protonated T18⋅A20(+) ⋅G5 base triple and other capping structural elements that provide novel insight into structural polymorphism and heterogeneity of G-quadruplexes in general. Specific stacking interactions amongst two G-quartets flanking base triples and base pairs in TD and KDH(+) forms are reflected in 10 K higher thermal stability of KDH(+) . Populations of TD and KDH(+) forms are controlled by pH. The (de)protonation of A20 is the key for pH driven structural transformation of htel1-ΔG23. Reversibility offers possibilities for its utilization as a conformational switch within different compartments of living cell enabling specific ligand and protein interactions.
authors.affiliation: Slovenian NMR Center, National Institute of Chemistry, Hajdrihova 19, Ljubljana, Slovenia.
authors.forename: Petra
authors.initials: P
authors.lastname: Galer
authors.affiliation: Slovenian NMR Center, National Institute of Chemistry, Hajdrihova 19, Ljubljana, Slovenia.
authors.forename: Baifan
authors.initials: B
authors.lastname: Wang
authors.affiliation: Slovenian NMR Center, National Institute of Chemistry, Hajdrihova 19, Ljubljana, Slovenia. primoz.sket@ki.si.|EN-FIST Center of Excellence, Trg OF 13, 1000, Ljubljana, Slovenia. primoz.sket@ki.si.
authors.forename: Primož
authors.initials: P
authors.lastname: Šket
authors.affiliation: Slovenian NMR Center, National Institute of Chemistry, Hajdrihova 19, Ljubljana, Slovenia. janez.plavec@ki.si.|EN-FIST Center of Excellence, Trg OF 13, 1000, Ljubljana, Slovenia. janez.plavec@ki.si.|Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, Ljubljana, Slovenia. janez.plavec@ki.si.
authors.forename: Janez
authors.initials: J
authors.lastname: Plavec
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D054856:G-Quadruplexes; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016615:Telomere / Q000737:chemistry* / Q000235:genetics
chemical_list: D004247:DNA
keywords: DNA; G-quadruplexes; NMR spectroscopy; human telomere repeat; topology