The specificity of base-pair substitution induced by the mutL and mutS mutators in E. coli.

The Escherichia coli mutator alleles, mutL and mutS, produced transversion as well as transition base-pair substitutions with the trpA reversion system. Transversions, however, were generally mutator-induced at a lower level than transitions and the specific type of transversion and its nucleotide position appeared to strongly affect its level of enhancement. These results are interpreted to mean that mutL- and mutS-dependent mismatch correction is generally more effective at correcting transition mispairings than transversion mispairings. Correction of transversion mispairings is probably dependent upon site of occurrence and type of mismatch.