ATP synthase

Question 1

What are the proteins used for the proton gradient of ATP synthesis?

Answer 1

F1 peripheral membrane protein and Fo integral membrane protein (where inhibitor oligomycin binds)

Question 2

What does F1 include?

Answer 2

9 subunits - 3a, 3B, Y, S, E

Question 3

a and B are identical or different?

Answer 3

identical

Question 4

What is B the catalytic site for?

Answer 4

ATP synthesis

Question 5

What does Y form and what does it effect?

Answer 5

stalk in the middle of the a3B3 complex and attacks F1 c ring of Fo

Question 6

What does Fo include?

Answer 6

A, b2, c8-17

Question 7

What is A

Answer 7

wraps around c10 ring and has 2 half channels

Question 8

what does b2 act through?

Answer 8

S -> a3B3

Question 9

What AA does c8-17 have?

Answer 9

Arg and Asp

Question 10

What is ATP tightly bound to?
What is needed to release the ATP

Answer 10

Active site
Energy from proton gradient

Question 11

What must ATP synthase must overcome to release ATP? What kind of catalysis is used

Answer 11

ATP synthase must overcome the large energy barrier
Rotational

Question 12

What are the three conformations B subunits cycle through?

Answer 12

Loose - binds ADP and Pi
Tight - ATP is formed
Open - ATP is released

Question 13

How does the B subunits cycle?

Answer 13

Y interacts asymmetrically allowing the B subunits to have different conformations. Each with a 120 degree turn of the Y subunit.

Question 14

What is involved in the stator arm?

Answer 14

A, b, S and a3B3 is stationary

Question 15

What is involved in the rotor?

Answer 15

C subunit ring rotates with respect to stator arm and proton gradient

Question 16

Pulling apart ATP from active site takes a lot of ….?

Answer 16

Free energy

Question 17

Where does the passage for movement of protons across the two half channels take place?

Answer 17

A subunit - no direct route from half channels

Question 18

1st half channel

Answer 18

IMM -> A subunit

Question 19

2nd half channel

Answer 19

inside A subunit-> matrix

Question 20

Half channel overview

Answer 20

1st half (IMM) -> protons must jump from A -> c subunit (ride around) -> 2nd half (matrix)

Question 21

Passage of protons that make C ring rotate (stroy):
C10 ring is held by ____ interactions.
Protons jump from IMM ____ from A –> C protonating ____ breaking the ____ interaction.
Now the C10 ring rotates so the protonated ____ moves away from ____ and into the _____ part of the membrane.
Simultaneously another c subunit is forced into contact with the _____ _______ of A and the proton that is carried by ____ is released into the ____.
This process continues.

Answer 21

ionic
first channel, Asp 61, ionic
c, A, hydrophobic
half channel, Asp, matrix

Question 22

What is the P/O ratio?

Answer 22

number of moles if ATP synthesis per mole O2 reduced to H2O
or
per mole of NADH/FADH2 oxidized

Question 23

What is the theoretical yield for NADH? Why is it less than this?

Answer 23

3
some proton gradient energy is not only used for ATP synthesis - powers the transport of solutes across IMM

Question 24

Calculating P/O ratio for NADH ~2.5

Answer 24

of protons pumped by NADH = 10 (if FADH2 this would be 6), # of ATPs produced per NADH = 1/4.3x10 =2.3ATP

moles to make c ring turn = 10 + 3 ATPs formed = 13
Total cost to synthesize 1 ATP = 13/3 = 4.3 (calculating O). The number or protons pumped by NADH is 10 (if FADH2 it would be 6), number of ATPs produced = 1/4.3x10 = 2.3 ATPs

Question 25

What would happen if the subunits in the c ring were less than 10?

Answer 25

NADH and FADH2 would increase and vice versa for greater than 10