The 180 exchange experiment ATP+HoO The AGo for AtP Readily rever sibl reactions lr I I synthesis on purified ADP Fi is close to zero 18 O (Paul Boyer) 18O-P=180 O Enzyme (F1)
The 18O exchange experiment : The G` 0 for ATP synthesis on purified F1 is close to zero! (Paul Boyer) Readily reversible reactions Keq = 2.4 G`0 = 0
80 60 P ADP+Pi ATP 40 ES [E·ATP] (in solution) 20 E·ADP+P1 长 0 E+S Reaction coordinate ypical ATP synthase enzyme Release of afp from atP synthase was proposed to be the major energy barrier for ATP synthesis
Release of ATP from ATP synthase was proposed to be the major energy barrier for ATP synthesis
15. ATP synthase comprises a proton channel (fo and a atPase (fu The Fi part consists of nine subunits of five types C3B368. The knoblike Fi 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 The Fo portion consists three types of subunits ab 210-12 The c subunits, each forming two transmembrane helices, form a donut-shaped ring in the plane of the membrane
15. ATP synthase comprises a proton channel (Fo ) and a ATPase (F1 ) • 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
The leg-and-foot-shaped yE subunits stands firmly on the ring of c subunits The two b subunits of Fo seem to connect to the aB hexamer via the s subunit of f 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 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 ten c subunits of f The yeast FoF structure) The y subunit of F The ATP synthase I comprises a proton adkrdasaisn channel (f ) and a t ATPase(F1) (n H+
The ATP synthase comprises a proton channel (Fo ) and a ATPase (F1 ) The ten c subunits of Fo The g subunit of F1 a b (The yeast FoF1 structure)