The ATP synthase is a nanomachine found in the inner mitochondrial membranes, chloroplasts, and bacterial cell membranes. It uses the energy from proton gradients across the membranes to produce ATP through rotary catalysis. The ATP synthase comprises two main parts - the F0 membrane-spanning portion that facilitates proton transport, and the F1 portion that extends into the matrix or cytoplasm and houses the catalytic sites to synthesize ATP. It can rotate at 8000 revolutions per minute to generate 3 ATP molecules per turn, and each ATP synthase can produce around 400 ATP molecules per second. The ATP synthase is an ancient enzyme that all cells rely on to generate energy through oxidative phosphorylation or photosynthesis.

1. ATP synthase
Muhammad
Shahjahan
Dr. Shabana

2. The ATP Synthase Is a Nanomachine that
Produces ATP by
Rotary Catalysis
– The ATP synthase (or F1F0 ATPase and also referred to as complex V) uses the
free energy of an electrochemical gradient of protons (or sodium ions)
generated by the respiratory chain to synthesize ATP.
– The ATP synthases comprise a very large group of highly conserved enzymes
that are found in the bacterial cytoplasmic membranes, the thylakoid
membranes of chloroplasts, and the inner membranes of mitochondria.

3. Structure of ATP Synthase
– 23 separate protein subunits
– Mass: 600,000 daltons
– Forward direction: ADP3-+P2-i+nH+P<=>ATP4-+H2O+(n-1)H+N
– Reverse direction: ATP4−+H2O<=>ADP3−+Pi2-+H+
– To distinguish it from other enzymes that hydrolyze ATP, it is also called an F1Fo ATP synthase or
F-type ATPase
– The F0 part, bound to inner mitochondrial membrane is involved in proton translocation
– F1 part found in the mitochondrial matrix is the water soluble catalytic domain.

4. – E.coli ATPase/synthase comprises of 8 different subunits.
– The chloroplast ATPase has two isoforms and in the mitochondria it has 7-9
additional subunits.
– 8000 revolutions per minute, generating three molecules of ATP per turn.
– Each ATP synthase can produce roughly 400 molecules of ATP per second.

9. Proton-driven Turbines Are of
Ancient Origin
– The mitochondrial ATP synthase is of ancient origin: essentially the same enzyme occurs in plant
chloroplasts and in the plasma membrane of bacteria or archaea.
– The main difference between them is the number of c subunits in the rotor ring.
– In mammalian mitochondria, the ring has 8 subunits
– In yeast mitochondria, the number is 10
– In bacteria and archaea, it ranges from 11 to 13
– In plant chloroplasts, there are 14
– cyanobacteria contain 15 c subunits.

10. Reverse ATP Synthase
– In principle, ATP synthase can also run in reverse as an ATP-powered proton
pump
– Converts the energy of ATP back into a proton gradient across the membrane.
– In many bacteria, the rotor of the ATP synthase in the plasma membrane
changes direction routinely.
– Aerobic respiration: ATP synthesis mode
– Anaerobic metabolism: ATP hydrolysis mode

11. – ATP hydrolysis serves to maintain the proton gradient across the plasma
membrane
– Power many other essential cell functions including nutrient transport and the
rotation of bacterial flagella
– F-type ATP synthases: Forward reaction
– V-type ATP synthases: Reverse reaction

12. Problems