The structure of F1-ATPase from Saccharomyces cerevisiae inhibited by its regulatory protein IF1

The structure of F-1-ATPase from Saccharomyces cerevisiae inhibited by the yeast IF1 has been determined at 2.5 angstrom resolution. The inhibitory region of IF1 from residues 1 to 36 is entrapped between the C-terminal domains of the alpha(DP)- and beta(DP)-subunits in one of the three catalytic interfaces of the enzyme. Although the structure of the inhibited complex is similar to that of the bovine-inhibited complex, there are significant differences between the structures of the inhibitors and their detailed interactions with F-1-ATPase. However, the most significant difference is in the nucleotide occupancy of the catalytic beta(E)-subunits. The nucleotide binding site in beta(E)-subunit in the yeast complex contains an ADP molecule without an accompanying magnesium ion, whereas it is unoccupied in the bovine complex. Thus, the structure provides further evidence of sequential product release, with the phosphate and the magnesium ion released before the ADP molecule.