title: Metal binding induces conversion of B- to the hybrid B-Z-form in natural DNA.
abstract: Highly polymerized herring testis DNA of the random nucleotide sequence has been studied in solution by circular dichroism and ultra-violet absorption spectrometry under various experimental conditions. At low temperature upon addition of 0.05 M NaCl or 1.15 M MgSO4 the DNA formed a helix that belonged to the B-family. As the temperature was increased a transition from the pure B- to the hybrid B-Z-form occurred in the presence of 1.15 M MgSO4. This transition occurred over a large range of temperatures and corresponded to a non-cooperative conformational change. A similar DNA transition was induced with 0.098 mM Co(NH3)6Cl3. However, in the presence of 5.3 M NaCl the DNA conformation was not similar to that observed in 1.15 M MgSO4 or 0.098 mM Co(NH3)6Cl3 independently on the environmental temperature. In 5.3 M NaCl the DNA is thought to undergo a transition from one to another right-handed conformation that could be intermediate partially dehydrated conformer arising on the first step in the sequential transition to the dehydration of the polynucleotide. Our results show that a realistic model of native DNA, bearing Z-tracts embedded in B-helixes, can be obtained upon binding of alkaline earth or transition metals.
authors.affiliation: Department of Microbiology, Kazan State University, Kremliovskaya st. 18, Kazan 420008, Russia. Maria.Filimonova@ksu.ru
authors.forename: Maria
authors.initials: M
authors.lastname: Filimonova
authors.forename: Valentina
authors.initials: V
authors.lastname: Gubskaya
authors.forename: Rustem
authors.initials: R
authors.lastname: Davidov
authors.forename: Alexander
authors.initials: A
authors.lastname: Garusov
authors.forename: Il'dus
authors.initials: I
authors.lastname: Nuretdinov
mesh_terms: D000042:Absorption; D000818:Animals; D002942:Circular Dichroism; D003035:Cobalt / Q000494:pharmacology; D004247:DNA / Q000737:chemistry*; D043542:DNA, Z-Form / Q000737:chemistry*; D005399:Fishes / Q000033:anatomy & histology; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008670:Metals / Q000737:chemistry / Q000494:pharmacology*; D009690:Nucleic Acid Conformation / Q000187:drug effects*; D009691:Nucleic Acid Denaturation / Q000187:drug effects; D012964:Sodium / Q000494:pharmacology; D013056:Spectrophotometry, Ultraviolet; D013737:Testis
chemical_list: D043542:DNA, Z-Form; D008670:Metals; C030862:cobalt ammonium complex; D003035:Cobalt; D004247:DNA; D012964:Sodium; D008274:Magnesium