Figure 6.
Enzyme assays with the C. botulinum RNR. A, assay with 0.5 mm CDP as substrate and increasing concentrations of ATP as allosteric effector. B, assay with 0.5 mm GDP as substrate and a combination of 2 mm dTTP and an increasing concentrations of ATP as allosteric effectors. C, assay with 0.5 mm CDP as substrate and a combination of 1 mm ATP and increasing concentrations of dATP as allosteric effectors. D, assay with a combination of CDP, UDP, GDP, and ADP as substrates used at 0.5 mm each. The allosteric effectors used are indicated on the abscissa. The effectors were generally used at 100 μm each, except for ATPhigh and dATPlow, which were used at 4 mm and 1 μm, respectively. All assays were performed in a buffer containing 10 mm magnesium acetate, 10 mm DTT, and 20 mm Tris-HCl, pH 7.5, with 1 µg of R1- and 2 µg of R2 proteins. Each plot represents the average of at least three independent experiments with standard errors indicated.