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. 2009 Jan 9;284(2):1145–1154. doi: 10.1074/jbc.M806964200

FIGURE 5.

FIGURE 5.

MacA regulates the ATPase activity of MacB. A, time course for the change in Pi concentration, corresponding to the absorbance change of the 2-amino-6-mercapto-7-methylpurine riboside in A, where 2.3 μm MacB was mixed with 1 mm ATP in the absence (upper trace) and presence (lower trace) of an equivalent concentration of MacA. In the absence of MacA, MacB produced a phosphate (Pi) burst, with a rate and amplitude of 0.235 (±0.001) s-1 and 2.20 (±0.01) μm, respectively. MacB did not produce a Pi burst in the presence of MacA. B, steady-state rate of Pi production by MacB as a function of the ATP concentration in the absence (lower curve) and presence (upper curve) of an equivalent concentration of MacA. The data are characterized by Vmax and Km values of 8.9 (±0.7) nmol of ATP/mg MacB/min and 374 (±126) μm, respectively, for MacB alone; and of 12.3 (±0.5) nmol of ATP/mg MacB/min and 72 (±22) μm, respectively, for MacB in the presence of an equivalent concentration of MacA.