IF1 inhibition of mitochondrial F1-ATPase is correlated to entrapment of four adenine- or guanine-nucleotides including at least one triphosphate.

Summary This paper demonstrates that the inhibition of F1 ATPase activity by the natural inhibitor protein IF1 is correlated to triphosphate nucleotide entrapment in F1. The complete balance of nucleotides bound after preincubation with Mg-[α- 32 P]GTP or Mg-[α- 32 P]ATP, used to promote IF1 inhibition, has been established on purified F1 containing 0.7 mol of non-exchangeable endogenous nucleotides. As many as 4 mol of labelled guanine- or adenine- nucleotides are trapped in F1; at least one of these nucleotides is a triphosphate. On the contrary, in the absence of IF1, no triphosphate nucleotide is significantly retained and the diphosphate nucleotides bound are mainly exchangeable.