ATP binding and hydrolysis steps of the uni-site catalysis by the mitochondrial F1-ATPase are affected by inorganic phosphate

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. (C) 2010 Elsevier B.V. All rights reserved.