Role of α/β interface in F1 ATPase rotational catalysis probed by inhibitors and mutations

Abstract The F 1 sector of ATP synthase (F O F 1 ) synthesizes or hydrolyses ATP via a rotational catalysis mechanism that couples chemical reaction with subunit rotation. Phytopolyphenols such as curcumin can inhibit bulk phase F 1 ATPase activity by extending the catalytic dwell time during subunit rotation (Sekiya, M., Hisasaka, R., Iwamoto-Kihara, A., Futai, M., Nakanishi-Matsui, M., Biochem. Biophys. Res. Commun. 452 (2014) 940–944). Citreoviridin, a polyene α-pyrone mycotoxin isolated from Penicillium sp, also inhibits ATPase activity. Molecular docking and mutational analysis indicated that these compounds interact with a region near the β-subunit Arg398 residue that lies at the interface with the α-subunit. Binding of these inhibitors lowered the rotation rate and increased the duration of the catalytic dwell synergistically with substitution of β-subunit Ser174 to Phe (βS174F), which rendered the enzyme defective for conformational transmission between β-subunits of different catalytic stages. Furthermore, substitution of α-subunit Glu402 to Ala (αE402A) in the α/β-interface also decreased the rotation rate by increasing the duration of the catalytic dwell. Interestingly, this mutation restored the catalytic dwell of the βS174F variant to that of the wild-type enzyme. These results suggest that the α/β-interface is involved in conformational changes of the β-subunit during rotational catalysis.