FIG. 2.
MTase activity associated with native and mutated Dam of A. hydrophila SSU in the E. coli GM33 strain by the AdoMet assay. The cell extracts from E. coli strains containing pBAD plasmid (as a control), the pBAD/damAhSSU recombinant plasmid, pBAD/damD/A, and the pBAD/damY/A plasmid were prepared, and the ability of Dam to transfer methyl-3H groups from AdoMet to N6-methyladenine-free lambda DNA was measured (6). Three independent experiments were performed, and the arithmetic means ± standard deviations were plotted. The increase in MTase activity in the cell extracts of E. coli overproducing native Dam was statistically significant at all of the protein concentrations according to Student's t test, compared to the activity in E. coli cell extracts overproducing mutated Dam. cpm, counts per minute.