CHARACTERIZATION OF THE MUTT NUCLEOSIDE TRIPHOSPHATASE OF ESCHERICHIA-COLI

The mutT protein, which prevents A:T --> C:G transversions during DNA replication, has the following enzymatic properties. Although it prefers dGTP as a substrate, it hydrolyzes all of the canonical nucleoside triphosphates to some extent. It has no activity in the absence of divalent cations, is maximally activated by magnesium ions, and has a pH optimum of 9.0. Nucleoside triphosphates are hydrolyzed according to the following equation. dGTP --> dGMP + PPi Studies with nucleotide analogues suggest that the enzyme may prefer the syn rather than the anti conformation of the nucleoside triphosphates, which might explain the role it plays in preventing mutations.