In 1997 Noji, Yasuda, Yoshida, and Kinosita attach a fluorescent actin filament to the F1 part of ATP synthase and watch it turn under an optical microscope.
The Visitor stands beside that motor in the inner mitochondrial membrane.
A Motor You Can Watch
- Every chemical reaction in a cell runs through an enzyme. An enzyme's active site fits its substrate and flexes as the substrate arrives (induced fit). The page reports rate enhancements of up to 1017-fold over the uncatalyzed reaction.
- ATP synthase has two rotary units. F0 sits in the membrane and F1 sits in the matrix, joined by a central rotating shaft. Protons flowing through F0 turn the shaft. Each full turn lets F1 make three ATP.
- In the 1997 experiment the long actin filament slowed the motor to at most about 4 turns per second (Noji et al. 1997). With a 40 nm gold bead as the load, isolated F1 records about 130 turns per second at saturating ATP (Yasuda et al. 2001), roughly 7,800 rpm.
- In human mitochondria the central stalk turns about 100 times per second, roughly 6,000 rpm, and each full turn makes 3 ATP, so one enzyme makes about 300 ATP per second (Watt et al. 2010). Each third of a turn (120 degrees) pairs with one ATP.
- The human c-ring carries 8 subunits, so 8 protons drive each turn that makes 3 ATP, which is 2.7 protons per ATP (Watt et al. 2010).
- The parts: a c-ring rotor in F0, a catalytic head of alternating alpha and beta subunits, a gamma shaft, and a stator (the b2δ peripheral stalk) that holds the head steady.
- The page reports roughly 1021 ATP made every second in a human body, about 40 kg per day in a 70 kg adult.
The c-ring spins on its shaft and one ATP leaves each third of a turn. The site's machine page animates the rotary motor, the chaperone cage, and the kinesin walker: open the machine animations.
How many ATP does one full rotation make, how many turns per second does the mitochondrial motor complete, and how many protons does each ATP take?
Three ATP per full turn, one per 120-degree step, at about 100 turns per second (roughly 6,000 rpm). The 8-subunit human c-ring takes 8 protons per turn, which is 2.7 protons per ATP.
ATP synthase is a literal rotary machine with a rotor, shaft, and stator, turning about 100 times per second in human mitochondria and making 3 ATP per turn.
The Visitor lights node 06, the flagship node, and the map brightens.
See the map