Some of the molecular aspects of methyl-directed mismatch repair in E. coli have 
been characterized. These include: mismatch recognition by mutS protein in which 
different mispairs are bound with different affinities; the direct involvement 
of d(GATC) sites; and strand scission by mutH protein at d(GATC) sequences with 
strand selection based on methylation of the DNA at those sites. In addition, 
communication over a distance between a mismatch and d(GATC) sites has been 
implicated. Analysis of mismatch correction in a defined system (Lahue et al., 
unpublished) should provide a direct means to further molecular aspects of this 
process.