A Comparative study of Fe(II) and Fe(III) interactions with DNA duplex: major and minor grooves bindings.
The involvement of the Fe cations in autoxidation in cells and tissues is well documented. DNA is a major target in such reaction, and can chelate Fe cation in many ways. The present study was designed to examine the interaction of calf-thymus DNA with Fe(II) and Fe(III), in aqueous solution at pH 6.5 with cation/DNA (P) (P = phosphate) molar ratios (r) of 1:160 to 1:2. Capillary electrophoresis and Fourier transform infrared (FTIR) difference spectroscopic methods were used to determine the cation binding site, the binding constant, helix stability and DNA conformation in Fe-DNA complexes. Structural analysis showed that at low cation concentration (r = 1/80 and 1/40), Fe(II) binds DNA through guanine N-7 and the backbone PO(2) group with specific binding constants of K(G) = 5.40 x 10(4) M(1) and K(P) = 2.40 x 10(4) M(1). At higher cation content, Fe(II) bindings to adenine N-7 and thymine O-2 are included. The Fe(III) cation shows stronger interaction with DNA bases and the backbone phosphate group. At low cation concentration (r = 1:80), Fe(III) binds mainly to the backbone phosphate group, while at higher metal ion content, cation binding to both guanine N-7 atom and the backbone phosphate group is prevailing with specific binding constants of K(G) = 1.36 x 10(5) M(-1) and K(P) = 5.50 x 10(4) M(-1). At r = 1:10, Fe(II) binding causes a minor helix destabilization, whereas Fe(III) induces DNA condensation. No major DNA conformational changes occurred upon iron complexation and DNA remains in the B-family structure.
Ouameur
A Ahmed
AA
Department of Chemistry-Biology, University of Québec at Trois-Rivières, Quebec, Canada.
Arakawa
H
H
Ahmad
R
R
Naoui
M
M
Tajmir-Riahi
H A
HA
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002412:Cations / Q000737:chemistry; D002417:Cattle; D004247:DNA / Q000737:chemistry*; D019075:Electrophoresis, Capillary; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D017550:Spectroscopy, Fourier Transform Infrared
D002412:Cations; D005290:Ferric Compounds; D005296:Ferrous Compounds; D004247:DNA