o A closed membrane system is essential for ATP synthesis but not for the electron flow(tested with detergent or physical 八化学渗透学说的实验证据 Shearing o Hydrophobic weak acids (DNP and FCCP) and ionophores(valinomycin) were found to be able to uncouple atp synthesis from electron transferring o The transmembrane proton pumping has been experimentally detected: pH in the intermembrane space was found to decrease when electron flow occurs (more protons are pumped when NADH rather than succinate. is utilized as reductant)
八 化 学 渗 透 学 说 的 实 验 证 据 A closed membrane system is essential for ATP synthesis but not for the electron flow (tested with detergent or physical shearing. Hydrophobic weak acids (DNP and FCCP) and ionophores (valinomycin) were found to be able to uncouple ATP synthesis from electron transferring. The transmembrane proton pumping has been experimentally detected: pH in the intermembrane space was found to decrease when electron flow occurs (more protons are pumped when NADH, rather than succinate, is utilized as reductant)
o An artificially imposed electrochemical gradient across the chloroplast thylakoid membrane and inner mitochondrial membrane alone(both were performed using sub-organelle vesicles) were found to drive ATP synthesis (with the ATP synthase present e The across-membrane proton gradient was thus finally accepted as the driving force for ATP synthesis: the chemiosmotic model was accepted as a theory! o The chemiosmotic theory unified the apparently disparate energy transduction processes as oxidative phosphorylation, photophosphory lation, active transport across membrane and the motion of bacterial flagella
An artificially imposed electrochemical gradient across the chloroplast thylakoid membrane and inner mitochondrial membrane alone (both were performed using sub-organelle vesicles) were found to drive ATP synthesis (with the ATP synthase present). The across-membrane proton gradient was thus finally accepted as the driving force for ATP synthesis: the chemiosmotic model was accepted as a theory! The chemiosmotic theory unified the apparently disparate energy transduction processes as oxidative phosphorylation, photophosphorylation, active transport across membrane and the motion of bacterial flagella
ATP synthase comprises a proton channel (Fo and a atPase(fu e The F, part consists of nine subunits of five types aBB3r68 e The knoblike F, portion is a hexamer of alternating a and B subunits(arranged like the segments of an orange), which sits atop the single rod-shaped y subunit e The Fo portion consists three types of subunits ab2C10-12 e The c subunits, each forming two transmembrane helices, form a donut-shaped ring in the plane of the membrane
The F1 part consists of nine subunits of five types: a3b3 gde. The knoblike F1 portion is a hexamer of alternating a and b subunits (arranged like the segments of an orange), which sits atop the single rod-shaped g subunit. The Fo portion consists three types of subunits: ab2 c10-12. The c subunits, each forming two transmembrane helices, form a donut-shaped ring in the plane of the membrane. ATP synthase comprises a proton channel (Fo ) and a ATPase (F1 )
e The leg-and-foot-shaped yc subunits stands firmly on the ring of c subunits e The two b subunits of f seem to connect to the aB hexamer via the 8 subunit ofFI e The proton channel is believed to lie between the a subunit and the ring of c subunits e X-ray crystallography revealed that the three B subunits of f assumes three different conformations with bound ADP, ATP analog, or empty respectively (John Walker, 1994, Nature 370:621-628!
The leg-and-foot-shaped ge subunits stands firmly on the ring of c subunits. The two b subunits of Fo seem to connect to the ab hexamer via the d subunit of F1 . The proton channel is believed to lie between the a subunit and the ring of c subunits. X-ray crystallography revealed that the three b subunits of F1 assumes three different conformations, with bound ADP, ATP analog, or empty respectively (John Walker, 1994, Nature, 370:621-628)!
The binding-change model was proposed to explain the action mechanism of ATP synthase e The model was proposed by Paul boyer in 1973 (PNAS, 70: 2837-2839), based on kinetic and binding studies( before the 3-D structure of bovine f,or yeast FoFI was determined) e Downhill proton movement through Fo will drive the rotation of the c-subunit ring and the asymmetrical γ subunits, which will cause each of the threeβ subunits to interconvert between the three conformations as a result each of them take turns to take up adp+ pi synthesize atp, and release atP
The binding-change model was proposed to explain the action mechanism of ATP synthase The model was proposed by Paul Boyer in 1973 (PNAS, 70:2837-2839), based on kinetic and binding studies (before the 3-D structure of bovine F1 or yeast FoF1 was determined). Downhill proton movement through Fo will drive the rotation of the c-subunit ring and the asymmetrical g subunits, which will cause each of the three b subunits to interconvert between the three conformations, as a result, each of them take turns to take up ADP + Pi , synthesize ATP, and release ATP