ATP synthase turns a flow of protons into ATP. Protons cross the membrane through the Fo motor and spin a ring of c subunits. The ring turns a central stalk inside the F1 head. Each 120° turn of the stalk changes the shape of the three catalytic β subunits and releases one ATP.
~100 turns/s
Turn rate in mitochondria
9An estimate quoted from earlier work, not a direct measurement
3
One per β subunit
2.7
c8 ring: 8 protons for 3 ATP
8–15 c subunits
c-ring size across species
9From c8 in animal mitochondria to c15 in Spirulina (Pogoryelov et al. 2009)
>40 pN·nm
Measured under high load in ATP hydrolysis
120° = ~80° + ~40°
Substeps seen in hydrolysis. First reported as about 90° + 30° (Yasuda et al. 2001)
~130 turns/s
α3β3γ subcomplex of thermophilic Bacillus F1, saturating ATP, 23 °C
≈ ΔG of one ATP
Near-complete energy conversion in F1