Postreplication repair prokaryotes

See also Postreplication Repair, Recombinational Repair, Prokaryotic Mismatch Repair, Eukaryotic Mismatch Repair, SOS Regulon (from Chapter 26)... 

See also Prokaryotic Mismatch Repair, Postreplication Repair... 

Fig. 1. Comparison of the DNA postreplication repair response in prokaryotes and eukaryotes. Shaded blocks indicate functionally conserved steps between the Escherichia coli and Saccharomyces cerevisiae pathways.

Postreplicational mismatch repair has been found to correct errors in base substitution occurring during DNA replication in prokaryotes.48 This lowers the error rate for the polymerase from 1 in 106 to 107 to the observed range of values of 1 in 108 to 1010 in E. coli. How does the repair system know in this case which base in a mispair is the incorrect one The answer appears to be that the parent strand is tagged by methylation. A small proportion, some 0.2%, of the cytosine residues are methylated at the 5 position, and a similar proportion of the adenine residues are methylated at the 6 position. As methylation is a postreplicative event, the daughter strand is temporarily undermethylated after replication. 

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