Cobalt-bleomycins and deoxyribonucleic acid: Sequence-dependent interactions, action spectrum for nicking, and indifference to oxygen

C. H. Chang, C. F. Meares

Research output: Contribution to journalArticle

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Abstract

Light-induced strand scission of DNA by cobalt-bleomycins is more likely to occur at certain base sequences than others. By use of 32P-end-labeled DNA restriction fragments as the substrates for cleavage, products have been analyzed on high-resolution polyacrylamide gels and compared to those produced by iron-bleomycin. The results indicate that the sites of damage to DNA are similar in both cases: pyrimidine residues located at the 3′ side of a guanine are preferentially attacked. Consistent with the observed nicking specificity, interactions between cobalt-bleomycin and guanine residues in the trinucleotide sequence GGT are revealed in a dimethyl sulfate methylation experiment. The action spectrum for the light-induced DNA cleavage reaction correlates with the absorption spectrum of cobalt-bleomycin in the wavelength range between 330 and 450 nm. In contrast to iron-bleomycin, the extent of DNA degradation by light-activated cobalt-bleomycins appears to be indifferent to the concentration of dissolved oxygen in the reaction medium, and little or no base propenal is produced. Bases (e.g., thymine) are released by both agents. Fluorescence quenching experiments show that apparent binding constants of cobalt-bleomycin complexes with DNA are in the 107 M-1 range in 25 mM tris(hydroxymethyl)aminomethane, pH 8, 1 mM NaCl, and 1 mM ethylenediaminetetraacetic acid at 25 °C.

Original languageEnglish (US)
Pages (from-to)2268-2274
Number of pages7
JournalBiochemistry
Volume23
Issue number10
StatePublished - 1984

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Oxygen
DNA
Guanine
Light
DNA Cleavage
Tromethamine
Thymine
Methylation
Edetic Acid
DNA Damage
Dissolved oxygen
Fluorescence
Action Spectrum
cobalt bleomycin
Absorption spectra
Quenching
Experiments
Degradation
Wavelength
Substrates

ASJC Scopus subject areas

  • Biochemistry

Cite this

Cobalt-bleomycins and deoxyribonucleic acid : Sequence-dependent interactions, action spectrum for nicking, and indifference to oxygen. / Chang, C. H.; Meares, C. F.

In: Biochemistry, Vol. 23, No. 10, 1984, p. 2268-2274.

Research output: Contribution to journalArticle

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