Figure 8.

[³H]Ouabain binding to chimera HN34/56 and rat Na⁺,K⁺-ATPase R113Q/D124N. The enzymes were incubated at 21°C in the presence of 5.0 mM MgCl₂/50 mM Tris-acetic acid, pH 7.0/1.0 mM ATP/100 mM NaCl/10 nM [³H]ouabain and varying concentrations of nonradioactive ouabain. The binding of [³H]ouabain in the absence of nonradioactive ouabain was set at 100%: NaKQN, 0.19 ± 0.03 pmol [³H]ouabain mg⁻¹ protein (■); HN34/56, 0.14 ± 0.03 pmol [³H]ouabain mg⁻¹ protein (○). Results are the average of three enzyme preparations.