Fig. 3.
SecYEG- and HTL-mediated stimulation of SecA ATPase activity is enhanced by CL. (A) Increasing amounts of SecYEG dimer (YEG2, open circles) or HTL complex (filled circles) were tested for their ability to activate the ATPase activity of SecA (0.3 µM) in the presence or absence of 40 µM CL. Data are representative of the mean of three independent experiments ± SD. Data were fitted as detailed in Materials and Methods. (B) Fluorescence quenching assays using fluorescein-tagged SecA (SecA795Fl) and SecYEG or HTL complex in the presence or absence of 40 µM CL. (Inset) The Kd values determined with and without CL. Note that the values of the Kd in the presence of CL are too low to be determined accurately. (C) Translocation ATPase activity of SecA as a function of substrate concentration (Upper) showing the average of three experiments fitted to the weak binding equation with y axis offset (SI Materials and Methods) and the corresponding translocation yields (Lower, with above representative blot) ± SEM.