Role of dam methylase in bacteria In bacteria, an enzyme called dam methylase (Deoxyadenosine methylase) methylates adenines (A) in the sequence GATC in the new strand formed after replication. What role does this methylation play? I read that it has something to do with proofreading. If this is so, then how?

The dam methylase has three different functions:

1. Correction replication errors, since the new DNA molecule is only hemimethylated (the old strand is methylated, the newly synthesized is not). Since the proof-reading only takes place on the new strand, errors introduced during replication can be corrected.
2. Regulation of replication: The ori of the chromosome is methylated to ensure that is only replicated once.
3. Regulation of transcription: Methylation of GATC sequences promote the transcription of genes.



For further details see the references.

References:

1. The great GATC: DNA methylation in E. coli
2. The dam and dcm strains of Escherichia coli--a review.
3. Dam methylation: coordinating cellular processes.