FIGURE 2.
Cys52, Cys206, and Cys215 are essential for the recycling of Cd-MsrA through the Trx/TrxR pathway. A, in the presence of l-Met-SO and the Trx/TrxR pathway, consumption of NADPH at varying concentrations of Cd-MsrA is shown. Cd-MsrA concentrations of 100, 200, 300, and 400 nm result in initial velocities of 4.2, 7.7, 9.9, and 15 milliabsorbance units/min, respectively. B, increasing the Trx/TrxR concentrations from 3/6 μm to 5/10 μm had no effect on initial velocities. C, Cd-MsrA follows Michaelis-Menten kinetics when coupled to the Trx/TrxR pathway. The plot of vi/E0 versus substrate concentration is shown. The data are presented as a mean ± S.D. (error bars) of at least two independent experiments. D, progress curves obtained using the WT and four Cys to Ser mutants of Cd-MsrA coupled to the Trx/TrxR pathway are shown.