The energy transmission in ATP synthase: from the gamma-c rotor to the alpha 3 beta 3 oligomer fixed by OSCP-b stator via the beta DELSEED sequence.
ATP synthase (F0F1) is driven by an electrochemical potential of H+ (delta microH+). F0F1 is composed of an ion-conducting portion (F0) and a catalytic portion (F1). The subunit composition of F1 is a alpha 3 beta 3 gamma delta epsilon. The active alpha 3 beta 3 oligomer, characterized by X-ray crystallography, has been obtained only from thermophilic F1 (TF1). We proposed in 1984 that ATP is released from the catalytic site (C site) by a conformational change induced by the beta DELSEED sequence via gamma delta epsilon-F0. In fact, cross-linking of beta DELSEED to gamma stopped the ATP-driven rotation of gamma in the center of alpha 3 beta 3. The torque of the rotation is estimated to be 420 pN x A from the delta microH+ and H(+)-current through F0F1. The angular velocity (omega) of gamma is the rate-limiting step, because delta microH+ increased the Vmax of H+ current through F0, but not the Km(ATP). The rotational unit of F0 (= ab2c10) is pi/5, while that in alpha 3 beta 3 is 2 pi/3. This difference is overcome by an analog-digital conversion via elasticity around beta DELSEED with a threshold to release ATP. The alpha beta distance at the C site is about 9.6 A (2,8-diN3-ATP), and tight Mg-ATP binding in alpha 3 beta 3 gamma was shown by ESR. The rotational relaxation of TF1 is too rapid (phi = 100 nsec), but the rate of AT(D)P-induced conformational change of alpha 3 beta 3 measured with a synchrotron is close to omega. The ATP bound between the P-loop and beta E188 is released by the shift of beta DELSEED from gamma RGL. Considering the viscosity resistance and inertia of the free rotor (gamma-c), there may be a stator containing OSCP (= delta of TF1) and F0-d to hold free rotation of alpha 3 beta 3.
Kagawa
Y
Y
Department of Biochemistry, Jichi Medical School, Tochigi-ken 329-04, Japan.
Hamamoto
T
T
D000595:Amino Acid Sequence; D004734:Energy Metabolism; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism*
D006180:Proton-Translocating ATPases