Mutational, NMR, and NH exchange studies of the tight and selective binding of 8-oxo-dGMP by the MutT pyrophosphohydrolase

The solution structure of the ternary MutT enzyme-Mg(2+)-8-oxo-dGMP complex showed the proximity of Asn119 and Arg78 and the modified purine ring of 8-oxo-dGMP, suggesting specific roles for these residues in the tight and selective binding of this nucleotide product Massiah, M. A., Saraswat, V., Azurmendi, H. F., and Mildvan, A. S. (2003) Biochemistry 42, 10140-10154]. These roles are here tested by mutagenesis. The N119A, N119D, R78K, and R78A single mutations and the R78K/N119A double mutant showed very small effects on k(cat) (