Another example of direct reversal is the removal of the methyl group from the methylated base O6 –methylguanine In this case, a methyltransferase removes the methyl group from the guanine residue by transferring it to one of its own cysteine residues. This is costly to the cell because the methyltransferase is not catalytic; having once accepted a methyl group, it cannot be used again.
#Unit 3. Fundamental Processes#DNA damage and repair mechanisms#Part B Pointers
