FIG. 5.

Hyperthermophilicity of M.PabI. All series of experiments illustrated by this figure were carried out at least three times to assess their reproducibility. (A) Reduction of M.PabI activity by heat was assessed after preincubating at 75°C (circles), 85°C (triangles), or 95°C (squares). An aliquot of purified M.PabI was heated in the enzyme dilution buffer at a 1.5 μM concentration of protein before the methylation reaction. The remaining activities relative to the intact methylation without preincubating were plotted with error bars indicating standard deviations. (B) Effects of incubation temperatures on the initial velocity of M.PabI reaction observed at 37°C (inverted triangles), 55°C (diamonds), 65°C (squares), 75°C (triangles), and 85°C (circles). The data obtained were plotted with error bars indicating standard deviations. (C) A continuous Arrhenius plot was obtained over a temperature range of 37 to 85°C from the initial velocities that were calculated as shown in panel B.