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

Abstract

The F1 sector of ATP synthase (FOF1) synthesizes or hydrolyses ATP via a rotational catalysis mechanism that couples chemical reaction with subunit rotation. Phytopolyphenols such as curcumin can inhibit bulk phase F1 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.