title: Different base/base mismatches are corrected with different efficiencies by the methyl-directed DNA mismatch-repair system of E. coli.
abstract: The efficiency of methyl-directed DNA mismatch-repair of E. coli acting in vivo on heteroduplex genomes of phage M13 was found to be strongly dependent on the nature of the base/base mismatch to be corrected. Three efficiency classes were characterized:high (T/G, C/A and G/G); intermediate (A/A); and low (G/A, A/G, T/T, C/C, C/T and T/C). Methyl-directed DNA mismatch repair was lost completely for any type of mismatch in strains carrying either mutL or mutS mutations. Data obtained with a mutH mutant suggest that this locus is involved in methyl-dependent DNA strand discrimination. A functional correlation is suggested between the differential repair efficiencies and the frequencies of the corresponding replication errors.
mesh_terms: D001482:Base Composition; D001483:Base Sequence; D003090:Coliphages / Q000235:genetics*; D004260:DNA Repair; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D005814:Genes, Viral; D008745:Methylation; D009154:Mutation
chemical_list: D004269:DNA, Bacterial