Lecture 8: ATP synthesis

Question 1

What are the two parts of ATPsynthase called?

Answer 1

F1 and F0

Question 2

What are the component parts of F1?

Answer 2

3 alpha
3 beta
1 gamma
1 delta
1 epsilon

Question 3

Which subunit binds F1 and F0 together?

Answer 3

Gamma

Question 4

Which subunit contains the catalytic site for ATP?

Answer 4

Beta

Question 5

What are the component parts of F0?

Answer 5

Three transmembrane subunits: a, b and c. They form an a1b2c9-10 (9 or 10 c parts dependent on species).
F0 also contains a, F6 and OSCP (antibiotics can kill bacteria by targeting this). The c subunits form a ring.

Question 6

Where is F1 situated and how does its composition suit this?

Answer 6

F1 is situated in the matrix and is water soluble as a result of being made up of hydrophilic polypeptides.

Question 7

Where is F0 situated and how does its composition suit this?

Answer 7

F0 is situated in the inner mitochondrial matrix and is hydrophobic.

Question 8

Describe the mechanism of ATP synthesis in 3 phases.

Answer 8

1) Translocation of H+s carried out by F0
2) Catalysis of formation of the phosphoanhydride bond of ATP carried out by F1
3) Coupling of the dissipation of the proton gradient with ATP synthesis, which requires interaction of F1 and F0.

Question 9

Which conformational shapes can the 3 protomers of the F1 exist in?

Answer 9

L, O and T
L = binds substrates/products loosely
O = does not bind anything
T = binds substrates/products tightly

Question 10

How do the protomers change conformation?

Answer 10

The energy stored in the electrochemical proton gradient is released when the protons are translocated into the matrix and is used to inter-convert these conformations.

Question 11

What is significant about the T conformation?

Answer 11

When ADP and Pi are in a protomer with the T conformation (tightly bound), minimum energy is required to synthesise the phosphoanhydride bond and make ATP.

Question 12

What happens to the ATP in the T protomer once it has been synthesised?

Answer 12

When the conformations change again, that protomer will take on the O conformation and ATP will be released.

Question 13

What is a stator?

Answer 13

It is the stationary part which a rotor is rotating with respect to.

Question 14

Which component parts make up the rotor in ATPsynthase?

Answer 14

Gamma, Epsilon- c12 ring complex

Question 15

Which component parts make up the stator in ATPsynthase?

Answer 15

ab2-alpha3,beta3,delta

Question 16

What causes the rotational movement of the rotor?

Answer 16

The passage of protons from the outside to the inside.

Question 17

What prevents the alpha3-beta3 assembly from rotating with the gamma subunit?

Answer 17

The b2-delta complex

Question 18

How do the protons cause rotation of the rotor?

Answer 18

The protons will bind to a c subunit (in F0) which interacts with the a subunit at a specific point of interaction. When the proton binds, this causes the c to rotate. It will stop rotating when it gets to a point where the c interacts with an a subunit again - almost a full rotation.