A helix-destabilizing protein substrate devoid of heterocyclic bases

Abstract

Summary A polynucleotide analog devoid of heterocyclic bases, poly(ribosylurea phosphate), was prepared by KMnO4 oxidation of poly(C). This analog binds effectively to seveal nucleic acid helix-destabilizing proteins, including gene 32 protein from T4 bacteriophage, UP1 from calf thymus, a protein from rat liver, and RNase A, which is a DNA helix-destabilizing protein. Binding was demonstrated by the ability of poly(ribosylurea phosphate) to inhibit protein-induced depression of polyd(A-T) Tm, as well as, in the case of the T4 and rat liver proteins, the quenching of intrinsic protein tryptophan fluorescence upon interaction with this polynucleotide analog. This substrate may prove useful in assessing the role that protein-ribose phosphate backbone interactions play in the binding specificity of helix-destabilizing proteins.