Molecular cloning and nucleotide sequence of the mutT mutator of Escherichia coli that causes A:T to C:G transversion.

The Escherichia coli mutator gene mutT, which causes A:T----C:G transversion, was cloned in pBR 322. mutT+ plasmids carry a 0.9 kb PvuII DNA fragment derived from the E. coli chromosome. Specific labelling of plasmid-encoded proteins by the maxicell method revealed that mutT codes for a polypeptide of about 15,000 daltons. The protein was overproduced when the mutT gene was placed under the control of the lac regulatory region on a multicopy runaway plasmid. The nucleotide sequence of the mutT gene was determined by the dideoxy method.