Interaction features of adenine DNA glycosylase MutY from E. coli with DNA substrates

Kinetic characteristics of specific recognition of damaged base by the DNA glycosylase MutY in model DNA substrates, containing oxoG/A-, G/A-, oxoG/C- and F/G pairs in the central position, were investigated. Conformational changes of the MutY enzyme during the recognition of the damaged base in DNA have been recorded by the change in the fluorescence intensity of tryptophan residues using the stopped-flow technique in real time. DNA duplexes containing a fluorescein residue were used for the registration of DNA conformational changes. Analysis of the kinetic curves allowed us to determine the values of rate constants for the kinetic stages of the interaction. It was shown that nonspecific contacts between the DNA-binding site of the enzyme and the DNA duplex are formed at the first stage of the interaction. It was found that the discrimination of Gua and oxoGua bases occurs at the second stage of the MutY interaction with the DNA duplex. The data obtained for the oxoG/C-substrate showed that the recognition of the base located opposite oxoGua also occurs at this stage.