ATP Synthase Flashcards
What are the two functional domains of ATP synthase
peripheral (F1) and integral (F0; meaning “oligomycin binding)
F1 consists of ____ subunits
9
F1 contains the catalytic site for _____ _____________ on each beta unit
ATP synthesis
What does the gamma subunit do in F1
forms a stalk in the centre of the a3b3 complex and (through epsilon subunit) attaches F1 to the membrane embedded C ring of F0
Each C subunit in the C ring of F0 contains _________ _______ residue in the middle of one of its helices
aspartic acid
The two beta subunits on F0 associate firmly with __________ (through the delta subunit of F1)
a3b3
The alpha subunit of F0 contains 2 __________ __________ and resides in the membrane, attached to the C ring, for movement of _______________
contains 2 half-channels
for movement of protons
The proton gradient drives release of ATP from the ________ _________
active site
How does ATP synthase overcome the large energy barrier for release of ATP
rotational catalysis
Boyer suggests that the ATP synthase active site cycles between a form of ___________ __________ of ATP to a form that ___________ ATP
form of tight binding of ATP to a form that releases ATP
Since the gamma subunit interacts _______________ with the a3b3 complex, the 3 beta subunits have different _______________ for different ATP binding sites
interacts asymmetrically
subunits have different conformations
What are the 3 conformations of the beta subunits
loose, tight, and open
What binds to the loose site
ADP + Pi
What binds to the tight site
ATP
What is released from the open site
ATP
What forms that stator arm
the alpha, beta, and gamma subunits of F1
The ring of C subunits rotates with respect to the _________ _________ powered by the proton gradient
stator arm
The gamma subunit turns __________ the core of the a3b3 complex
within (a3b3 doesn’t turn with it)
How do protons move through the ATP synthase enzyme
in the bottom half channel, around C ring, and out upper half channel
What are the steps that make the c-ring rotate
- the c-ring is held together by ionic interaction between asp 61 of “c” and two conserved arginine residues of “a”
- proton jumps from intermembrane space half channel of “a” to “c” and protonates Asp 61
- this breaks the ionic interaction between Asp and arginine, setting c-ring free
- 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
- the process repeats the amount of c-subunits within the ring (ie. C-10 would be 10 turns for a full rotation)
One full rotation of gamma (caused by rotation of c) results in…
beta subunits cycling through all three possible conformations
- leads to synthesis and release of ATP
One full turn of ATP synthase generates how many ATP
3 (because of 3 beta subunits)
What is the P/O of NADH
2.5
What is the P/O of FADH2
1.5
Why is the P/O value less than the theoretical value
not all of the proton gradient energy is gonna be used for ATP synthesis
