Cleavage of the glycosidic linkage of pyrimidine ribonucleosides by the bisulfite-oxygen system

When a solution containing 2 mM uridine, 20 mM sodium bisulfite, 0.1 mM MnCl(2), and 100 mM sodium phosphate buffer of pH 7.0 was incubated aerobically at 37° or 0°, partial cleavage of the glycosidic linkage of uridine took place. About 20% of the uridine was converted to uracil by the incubation for 4 hrs. Cytosine was produced from cytidine by similar treatment with bisulfite. These reactions were caused by free radicals generated by Mn(2+)-catalyzed autoxidation of bisulfite. Glycosidic bond cleavage by the bisulfite-oxygen system was not detected for adenosine, AMP, guanosine, GMP, thymidine, TMP, deoxyuridine, dCMP, dAMP, and dGMP. When poly(U) and poly(C) were treated with 20 mM sodium bisulfite in the same manner, chain fission of the polymer occurred as judged by the elution-pattern change in gel filtration through Sephadex columns. No change in the elution pattern was observed for bisulfite-treated poly(A), poly(U)· poly(A) or tRNA

The effect of bisulfite modification on the template activity of DNA for DNA polymerase I(1)

Cytosine residues of poly(C) and heat-denatured calf thymus DNA were transformed into 5,6-dihydrouracil-6-sulfonate (U(SO(−)(3))) residues by treatment with bisulfite. The poly(U(SO(−)(3))(2), C(3)) and poly(U(SO(−)(3))(9), C(1)) prepared did not form inter-base binding with either poly(A) or poly(I) as judged by the absence of hypochromicity in ultraviolet absorbance. U(SO(−)(3)) residues in the DNA inactivated it to serve as template for E.coli DNA polymerase I, while the template activity was restored by conversion of the U(SO(−)(3)) residues into U