Wayne Frasch
Professor and Faculty Leader
Biomedicine and Biotechnology Faculty Group
School of Life Sciences
P.O. Box 874501
Arizona State University
Tempe, AZ 85287-4501
frasch@asu.edu
(480) 965-8663
F₁Fₒ ATP Synthase
Single-molecule studies of rotation catalyzed by
F-type, A-type, and V-type molecular motors
The F₁Fₒ ATP synthase rotary motor uses a non-equilibrium transmembrane H⁺ gradient to drive CW rotation in Fₒ that forces F₁ to make 80% of cellular ATP.
At high [ATP], F₁-ATPase can drive CCW rotation that pumps H⁺ in the opposite direction.
We have developed novel single-molecule assays to investigate the mechanisms of these remarkable motors.
F-type, A/V-type, and V-type Rotary Motor Diversity
F₁-ATPase
All types contain 3 catalytic sites that operate in an alternating site mechanism. One ATP is synthesized (or hydrolyzed) for each 120° rotational power stroke.
Fₒ-motor
All types contain membrane proteins subunit-a and a ring of c-subunits. Subunit-a feeds H⁺ to/from each c-subunit to rotate the c-ring.
F-type ATP synthases (F₁Fₒ)
3 ATP are synthesized for each 360° rotation
Regulatory mechanisms limit ATPase activity
1 peripheral stator stalk
Mammals form F₁Fₒ dimers with c₈-rings to transport 8 H⁺ per 360° rotation
Single-celled eukaryotes transport 10 8 H⁺ per 360° rotation
Eubacterial c-rings vary from c₉ to c₁₇, and some use Na⁺ instead of H⁺
Chloroplasts have c₁₄-rings to make approximately half the ATP per unit energy than mammals
A-type (A₁Aₒ) archaeal, or A/V-type bacterial ATP synthases
3 ATP are synthesized for each 360° rotation
2 peripheral stator stalks
Some use a Na⁺ gradient instead of a H⁺ gradient
V-type vacuolar ATPases (V₁Vₒ-ATPases)
3 ATP are hydrolyzed for each 360° rotation to pump H⁺ into organelles
Incapable of ATP synthesis
3 peripheral stator stalks
Activity regulated by reversible dissociation of V₁ from Vₒ
Some c-subunits are incapable of H⁺ transport
