FIGURE 2.

Nucleotide binding to the catalytic sites of βR394A/βR398A/βQ441A mutant F₁. Nucleotide binding was measured by the decrease in fluorescence of the insertedβW331 residue. Closed symbols, βR394A/βR398A/βQ441A+βY331W F₁; open symbols, βY331W control. A, binding of MgATP; B, binding of MgADP; C, binding of the transition state analog MgADP·ScF_x. The lines are fits of theoretical curves to the measured data points, assuming three independent sites. For the resulting K_d values and further details, see text.