ATP binding and hydrolysis steps of the uni-site catalysis by the mitochondrial F 1-ATPase are affected by inorganic phosphate

Abstract

The effect of inorganic phosphate (P i) on uni-site ATP binding and hydrolysis by the nucleotide-depleted F 1-ATPase from beef heart mitochondria (ndMF 1) has been investigated. It is shown for the first time that P i decreases the apparent rate constant of uni-site ATP binding by ndMF 1 3-fold with the K d of 0.38 ± 0.14 mM. During uni-site ATP hydrolysis, P i also shifts equilibrium between bound ATP and ADP + P i in the direction of ATP synthesis with the K d of 0.17 ± 0.03 mM. However, 10 mM P i does not significantly affect ATP binding during multi-site catalysis.