In Escherichia coli and related bacteria, the very-short-patch (VSP) repair 
pathway uses an endonuclease, Vsr, to correct T-G mismatches that result from 
the deamination of 5-methylcytosines in DNA to C-G. The products of mutS and 
mutL, which are required for adenine methylation-directed mismatch repair (MMR), 
enhance VSP repair. Multicopy plasmids carrying mutS alleles that are dominant 
negative for MMR were tested for their effects on VSP repair. Some mutS 
mutations (class I) did not lower VSP repair in a mutS(+) background, and most 
class I mutations increased VSP repair in mutS cells more than plasmids 
containing mutS(+). Other plasmid-borne mutS mutations (class II) and mutS(+) 
decreased VSP repair in the mutS(+) background. Thus, MutS protein lacking 
functions required for MMR can still participate in VSP repair, and our results 
are consistent with a model in which MutS binds transiently to the mispair and 
then translocates away from the mispair to create a specialized structure that 
enhances the binding of Vsr.