FIG. 3.

ATPase activity of purified DotB. ATPase activity was determined by measuring the amount of free phosphate in the reaction by a colorimetric assay (EnzChek; Molecular Probes). (A) Standard curve showing absorbance at 360 nm as a function of the concentration of phosphate. (B) ATPase activity of the positive control apyrase. (C) ATPase activity of DotB (squares) and DotB K162Q (diamonds). The specific activities of apyrase and DotB were calculated to be 3.0 μmol/min/mg and 6.4 nmol/min/mg, respectively. Each point represents three replicates.