ATP synthase Flashcards
What are the proteins used for the proton gradient of ATP synthesis?
F1 peripheral membrane protein and Fo integral membrane protein (where inhibitor oligomycin binds)
What does F1 include?
9 subunits - 3a, 3B, Y, S, E
a and B are identical or different?
identical
What is B the catalytic site for?
ATP synthesis
What does Y form and what does it effect?
stalk in the middle of the a3B3 complex and attacks F1 c ring of Fo
What does Fo include?
A, b2, c8-17
What is A
wraps around c10 ring and has 2 half channels
what does b2 act through?
S -> a3B3
What AA does c8-17 have?
Arg and Asp
What is ATP tightly bound to?
What is needed to release the ATP
Active site
Energy from proton gradient
What must ATP synthase must overcome to release ATP? What kind of catalysis is used
ATP synthase must overcome the large energy barrier
Rotational
What are the three conformations B subunits cycle through?
Loose - binds ADP and Pi
Tight - ATP is formed
Open - ATP is released
How does the B subunits cycle?
Y interacts asymmetrically allowing the B subunits to have different conformations. Each with a 120 degree turn of the Y subunit.
What is involved in the stator arm?
A, b, S and a3B3 is stationary
What is involved in the rotor?
C subunit ring rotates with respect to stator arm and proton gradient
Pulling apart ATP from active site takes a lot of ….?
Free energy
Where does the passage for movement of protons across the two half channels take place?
A subunit - no direct route from half channels
1st half channel
IMM -> A subunit
2nd half channel
inside A subunit-> matrix
Half channel overview
1st half (IMM) -> protons must jump from A -> c subunit (ride around) -> 2nd half (matrix)
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.
ionic
first channel, Asp 61, ionic
c, A, hydrophobic
half channel, Asp, matrix
What is the P/O ratio?
number of moles if ATP synthesis per mole O2 reduced to H2O
or
per mole of NADH/FADH2 oxidized
What is the theoretical yield for NADH? Why is it less than this?
3
some proton gradient energy is not only used for ATP synthesis - powers the transport of solutes across IMM
Calculating P/O ratio for NADH ~2.5
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
What would happen if the subunits in the c ring were less than 10?
NADH and FADH2 would increase and vice versa for greater than 10
