Solution structure of a C-terminal coiled-coil domain from bovine IF1: the inhibitor protein of F1 ATPase

Bovine IF1 is a basic, 84 amino acid residue protein that inhibits the hydrolytic action of the F1F0 ATP synthase in mitochondria under anaerobic conditions. Its oligomerization state is dependent on pH. At a pH value below 6.5 it forms an active dimer. At higher pH values, two dimers associate to form an inactive tetramer. Here, we present the solution structure of a C-terminal fragment of IF1 (44–84) containing all five of the histidine residues present in the sequence. Most unusually, the molecule forms an anti-parallel coiled-coil in which three of the five histidine residues occupy key positions at the dimer interface.