ATP Synthase

Question 1

What are the two functional domains of ATP synthase

Answer 1

peripheral (F1) and integral (F0; meaning “oligomycin binding)

Question 2

F1 consists of ____ subunits

Answer 2

9

Question 3

F1 contains the catalytic site for _____ _____________ on each beta unit

Answer 3

ATP synthesis

Question 4

What does the gamma subunit do in F1

Answer 4

forms a stalk in the centre of the a3b3 complex and (through epsilon subunit) attaches F1 to the membrane embedded C ring of F0

Question 5

Each C subunit in the C ring of F0 contains _________ _______ residue in the middle of one of its helices

Answer 5

aspartic acid

Question 6

The two beta subunits on F0 associate firmly with __________ (through the delta subunit of F1)

Answer 6

a3b3

Question 7

The alpha subunit of F0 contains 2 __________ __________ and resides in the membrane, attached to the C ring, for movement of _______________

Answer 7

contains 2 half-channels
for movement of protons

Question 8

The proton gradient drives release of ATP from the ________ _________

Answer 8

active site

Question 9

How does ATP synthase overcome the large energy barrier for release of ATP

Answer 9

rotational catalysis

Question 10

Boyer suggests that the ATP synthase active site cycles between a form of ___________ __________ of ATP to a form that ___________ ATP

Answer 10

form of tight binding of ATP to a form that releases ATP

Question 11

Since the gamma subunit interacts _______________ with the a3b3 complex, the 3 beta subunits have different _______________ for different ATP binding sites

Answer 11

interacts asymmetrically
subunits have different conformations

Question 12

What are the 3 conformations of the beta subunits

Answer 12

loose, tight, and open

Question 13

What binds to the loose site

Answer 13

ADP + Pi

Question 14

What binds to the tight site

Answer 14

ATP

Question 15

What is released from the open site

Answer 15

ATP

Question 16

What forms that stator arm

Answer 16

the alpha, beta, and gamma subunits of F1

Question 17

The ring of C subunits rotates with respect to the _________ _________ powered by the proton gradient

Answer 17

stator arm

Question 18

The gamma subunit turns __________ the core of the a3b3 complex

Answer 18

within (a3b3 doesn’t turn with it)

Question 19

How do protons move through the ATP synthase enzyme

Answer 19

in the bottom half channel, around C ring, and out upper half channel

Question 20

What are the steps that make the c-ring rotate

Answer 20

1. the c-ring is held together by ionic interaction between asp 61 of “c” and two conserved arginine residues of “a”
2. proton jumps from intermembrane space half channel of “a” to “c” and protonates Asp 61
3. this breaks the ionic interaction between Asp and arginine, setting c-ring free
4. c-ring rotates so the protonated c is moving away from the “a”, simultaneously another “c” subunit (AspH) is forced into contact with the half channel of “a” and the proton is released from Asp into the half channel to be released into matrix
5. the process repeats the amount of c-subunits within the ring (ie. C-10 would be 10 turns for a full rotation)

Question 21

One full rotation of gamma (caused by rotation of c) results in…

Answer 21

beta subunits cycling through all three possible conformations
- leads to synthesis and release of ATP

Question 22

One full turn of ATP synthase generates how many ATP

Answer 22

3 (because of 3 beta subunits)

Question 23

What is the P/O of NADH

Answer 23

2.5

Question 24

What is the P/O of FADH2

Answer 24

1.5

Question 25

Why is the P/O value less than the theoretical value

Answer 25

not all of the proton gradient energy is gonna be used for ATP synthesis