The deoxyadenosine methylase (dam) enzyme of E. coli mediates the post-replicati
ID: 168468 • Letter: T
Question
The deoxyadenosine methylase (dam) enzyme of E. coli mediates the post-replicative methylation of newly synthesized DNA. The SeqA protein of E. coli binds with high affinity to hemi-methylated DNA to control the timing of the initiation of DNA replication. Suppose that the gene encoding the dam methylase acquired a mutation that dramatically increased the amount of methylase activity in the cell. How would the timing of initiation of the next round of replication beta affected by the mutation? Would the time required before the next round of DNA synthesis increase or decrease? A. It would decrease due to more persistent seqA binding. B. It would increase due to less persistent SeqA binding C. It would decrease due to less persistent SeqA binding D. It would increase due to more persistent SeqA binding E. It would not be affected.Explanation / Answer
DAM enzyme of E. coli is the main regulator for starting a new replication cycle. it causes hemimethylation to the newly synthesised nucleotide to distinguish them from parental one. seqA PROTEIN BIND WITH HIGH AFFINITY TO HEMIMETHYLATED DNA. If any mutation occur that increases dam expression then- the time required for next round of replication cycle will increase due to less persistant SeqA binding.
the over expression of DAM cause more methylation, but seqA BIND ONLY TO HEMIMETHYLATED 13mers in the GATC region. it neither bind to unmethylated or fully methylated. so it ultimately take more time to next cell cycle.
intrinsic binding instability of SeqA result in release of hemimethylated OriC.