FIGURE 2.

Effects of truncating or cross-linking the ϵCTD on inhibition of F₁(−δϵ). A, F₁(−δϵ) was preincubated for 10 min with 0.1 mm EDTA and ATP (black and orange symbols) or GTP (green symbols) and the indicated concentrations of wild-type H₆-ϵ (♦) or H₆-ϵ88stop (●). Hydrolysis was initiated by adding magnesium acetate. Final concentrations of added ligands were as follows: 2:1 mm ATP/Mg²⁺ (black); 1:2 mm ATP/Mg²⁺ (orange); 1:2 mm GTP/Mg²⁺ (green). B, ATPase assays as for A, but H₆-ϵA101C/L121C was used with 1 mm DTT present (▴) or with an ϵA101C–L121C disulfide bond (■). See “Experimental Procedures” for assay details and regression analysis. With H₆-ϵ88stop, data points are averages from three (ATP) or two (GTP) experiments, and standard error bars are included but are smaller than the symbols for most points. Results of regression analyses for these and for a data set with untagged WT ϵ are summarized in Table 1.