FIGURE 3.

Effects of temperature, salt, and mercury concentration on the catalytic activities of ATII-LCL and soil MerAs. A, thermostability. The ATII-LCL and soil MerAs were incubated at the indicated temperature for 10 min, and the residual enzymatic activities were assayed under standard conditions. B, effect of NaCl concentration on MerA activity. The enzymatic activities were measured in reaction mixtures containing the indicated concentrations of NaCl. C, sensitivity to HgCl₂. The enzymes were incubated in the assay mixture for 10 min, in the absence of NADPH and presence of the indicated concentrations of HgCl₂. The enzyme activities were then measured by addition of NADPH to the assay mixture. D, determination of the MIC for HgCl₂. Solutions containing increasing concentrations of HgCl₂ were placed in wells punched in LB-agar plates (supplemented with 50 μg/ml kanamycin and 1 mm isopropyl β-d-thiogalactoside) inoculated with E. coli transformants. The plates were incubated for 24 h at 37 °C. The radii of the clear zones are a measure of the toxic effect of HgCl₂ on bacterial growth.