BCH210H1 Lecture Notes - Lecture 30: Atp Synthase, Atp Hydrolysis, Integral Membrane Protein
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Lecture 30: ATP Synthesis
ATP Synthase
• F0 is the integral membrane protein unit that anchors the enzyme in the inner
mitochondrial membrane
- a subunits creates a channel where protons will enter and bind to c
subunit in the membrane (10-15 of them) which forms a ring and rotates
when protons bind to them
• Protons flow through a subunit causing a rotation in the ring c subunits of F0
• F1 is the peripheral protein (matrix) unit that carries out the catalytic synthesis of ATP
- 3 a and 3 B subunits (Bs are responsible for ATP synthesis)
- Y subunit that runs from membrane component to the middle of the protein (y rotates that induce
conformational change of B)
- Delta at the top and epsilon in the middle that help attachment of lollipop to membrane
• Stator (considered membrane component d) holds the membrane and lollipop together
• Conformational changes in the F1 B subunits are responsible for ATP synthesis
• ATP is then exported out of the matrix to cytosol for use in the rest of the cell by translocase
Boyer’s Binding Change Mechanism
• Each B subunit changes between 3 states (they catalyze ATP separately)
- Open or Empty/exit
- Loose with ADP and Pi bound
- Tight with ATP bound
1. Loose state – ADP + Pi can bind → conformational change through y touching c
2. Tight state – ATP is formed through ADP and Pi combination + H2O → another conformational change
3. Open/empty state → ATP released
• Constant flow of the H+ and rotation of gamma changes the conformation of each subunit
independently
• All three subunits will all be in different states
• A subunits also go through conformational change but do not participate in catalysis (part of complete
enzyme, binding to other two B)
ATP synthase is reversible
• Imaging techniques can be used to visualize rotation of the F1 unit
• ATP hydrolysis can be used to reverse the reaction mechanism
• ATP synthase could be used to drive proton transport via ATP hydrolysis
and drive rotation (proton pumping)
• Add his-tag to anchor F1 to Ni-NTA and label y with GFP → adding ATP + H2O, it binds to tight state,
hydrolysis takes (ADP + Pi) place with conformational change in B that also rotates y
ATP Synthase
• The B-subunit is responsible for ATP synthesis in the matrix of the mitochondria
• As protons flow through the c ring, rotation results in a conformational change in B via the y subunit
• 3 H+ are pumped per ATP molecule synthesized in cytosol (human ATP synthase)
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BCH210H1 Full Course Notes
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