Several classes of binding sites for metals and nucleotides on yeast mitochondrial oligomycin sensitive ATPase

The binding properties of Mg²⁺, Mn²⁺ to yeast mitochondrial oligomycin sensitive ATPase complex are studied, as reflected by their catalytic effect (hydrolysis of ATP or pNPP, a pseudo substrate) or by a physical parameter (atomic absorption, electron paramagnetic resonance of Mn²⁺, enhanced fluorescence of chelating chlorotetracyclin). At least two classes of sites with very different affinities respectively around 10⁻⁵ M and 10⁻⁴ M are demonstrated : high affinity sites for cations which participate in pNPP hydrolysis and can bind ADP or ATP, although they have a poor efficiency for ATP hydrolysis, and low affinity sites for cations which participate efficiently in both pNPP and ATP hydrolysis. The possibility that the tight site class has itself two sub-classes is also discussed.