The energy transmission in ATP synthase: From the γ-c rotor to the αβ oligomer fixed by OSCP-b stator via the βDELSEED sequence

ATP synthase (FF) is driven by an electrochemical potential of H (ΔμH). FF is composed of an ion-conducting portion (F) and a catalytic portion (F). The subunit composition of F is αβγδε. The active αβ oligomer, characterized by X-ray crystallography, has been obtained only from thermophilic F (TF). We proposed in 1984 that ATP is released from the catalytic site (C site) by a conformational change induced by the βDELSEED sequence via γδε-F. In fact, cross-linking of βDELSEED to y stopped the ATP-driven rotation of γ in the center of αβ. The torque of the rotation is estimated to be 420 pN·Å from the ΔμH and H-current through FF. The angular velocity (ω) of γ is the rate-limiting step, because ΔμH increased the V of H current through F, but not the K. The rotational unit of F (= abc) is π/5, while that in αβ is 2π/3. This difference is overcome by an analog-digital conversion via elasticity around βDELSEED with a threshold to release ATP. The αβ distance at the C site is about 9.6 Å (2,8-diN-ATP), and tight Mg-ATP binding in αβγ was shown by ESR. The rotational relaxation of TF is too rapid (φ = 100 nsec), but the rate of AT(D)P-induced conformational change of αβ measured with a synchrotron is close to ω. The ATP bound between the P-loop and βE188 is released by the shift of βDELSEED from γRGL. Considering the viscosity resistance and inertia of the free rotor (γ-c), there may be a stator containing OSCP (=δ of TF) and F-d to hold free rotation of αβ. © 1996 Plenum Publishing Corporation.