Lecture 11: Oxidative Phosphorylation: ATP Synthase

Question 1

What is the ATP synthase complex

Answer 1

a molecular motor

protein conf changes in response to proton motive force (proton gradient) across inner mitochondrial membrane

Question 2

Mitochondrial ATP synthase complex

Answer 2

uses proton motive force generated by ETS to synth ATP by conf changes in oxidative phoshorylation process

Question 3

where is the gamma subunit?

Answer 3

between the alpha and beta

Question 4

F1

Answer 4

catalytic activity

in matrix

Question 5

Fo

Answer 5

proton channel

in membrane

Question 6

Parts of the ATP synthase

Answer 6

rotor
catalytic head piece
stator

Question 7

Rotor

Answer 7

C components

turns 120 degrees for every 3H+ that corss the membrane through the c ring

Question 8

catalytic head piece

Answer 8

contains the 3 enzyme active sites in the beta subunit

Question 9

stator

Answer 9

alpha subunit that is made of 2 proton half channels

also stabalizing arm

Question 10

WHAT does the Fo component effect?

Answer 10

affinity of beta subunit for ATP

NOT rate of ATP synthesis

Question 11

what happens to the dissociation constant of ATP synthase in the presence of a proton motive force?

Answer 11

it INCREASES

we need a proton motive force to RELEASE ATP that has been synthesized

Question 12

Steps of the binding change mechanism

Answer 12

1. gamma subunit contacts all 3 beta subunits, leading to 3 dif confs in betas
2. ATP binding affinities of betas are: T, L, O
   3: for each 120 degree rotation, beta subunits sequenctially under go conf changes of O to L to T and again
3. binding change mech model says 1 full rotation will give THREE ATP

Question 13

what is bound in the… O conf

Answer 13

nada

Question 14

what is bound in the… L conf

Answer 14

ADP + Pi

Question 15

what is bound in the… T conf

Answer 15

ATP

Question 16

how to the confs change?

Answer 16

the betas don’t move!

gamma does, which changes the confs of the betas

Question 17

How many protons go through 1 rotation (120 degrees)

Answer 17

9! three per ATP and we get 3 ATP

Question 18

ATP synthase vs. ATP hydrolase

Answer 18

same complex!!!!!
catalyzes ATP synthesis and hyrdolysis

synthesis: protons move from intermembrane space to matrix
hydrolysis: protons move from matrix to IMS

Question 19

when can it be a ATP hydrolase

Answer 19

high concs of ATP
gamma subunit rotates in opposite direction
ATP goes to ADP + Pi

Question 20

how does proton movement in c ring cause gamma rotation

Answer 20

lots of c protein with ASPARTATE in middle
its more likely to be in its neutral conf in the hydrophobic part of membrane
when C ring is assembled with a subunit, the protons in the half channle in the a subunit can reach an aspartate in the c ring, which causes it to be charged and a conf change happens (SLIDE 17-18)