BIOL 201 Lecture Notes - Lecture 9: Leucanthemum Vulgare, Tempeh, Gladiolus
Composed of two fragments: F1 (hexameric head and shaft component)
and F0 (intermembrane components)
•
Head made of 3 alpha 3 beta subunits, where ATP is synthesized
•
Enter 1st helf channel --> around rotating C-ring --> second half
channel
○
Rotation of C ring causes simultaneous ATP synthesis
○
Coupling allowed by gamma subunit which rotates with C ring,
drives conformational changes in A/B subunits
○
Contains proton half channels, contains pKa- regulated residues where
protons flow through
•
ATP synthase harnesses the protonmotive force to make ATP
Arg residue with net + charge and glu residues that carry negative charge
that interacts with it
•
Proton enters and begins to interact with - residue, dislodges Arg
(favourable due to concentration gradient, different structures of
channels altering respective pKas)
•
Arg swings onto different (-) charge on adjacent c-ring subunit, dislodges
proton in 2nd half channel into matrix
•
C ring rotates- all charges have been neutralized once proton enters 1/2
channel and neutralizes negative residue
•
Arginine clicks back to subunit next to 1st half-channel
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Process repeats
•
10-14C subunits
•
Can only move in one direction due to pall moving up slope of blade
○
Couldn’t this convert thermal motion (random motion of propeller
blade) into potential energy (raising wait with ratchet)?
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must be "rectified" (INPUT ENERGY) to avoid breaking 2nd law of
thermodynamics - can't reduce entropy by converting thermal E to
work
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Pall is also vibrating, has equal probability
○
If you reverse the gradient, you reverse the motion!
▪
RECTIFICATION OF ATP SYNTHASE = PROTON CONCENTRATION
GRADIENT, provides POTENTIAL ENERGY INPUT!
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"Brownian Ratchet" - random motion is the only thing driving rotation
•
Recent cryo-EM has determined the structure of the c ring
•
The F0 subunit c ring rotates as protons pass through it
Active sites in B subunits, but alpha subunits still present
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Open: nucleotides pop in and out
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Loose: ADP + Pi trapped but non-reactive
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Tight: ADP + Pi converted (reversibly) to ATP
•
Dark green lobe interacts with B subunit to put it into the open
conformation
○
Second lobe causes tight conformation, butt end allows loose conformation
○
Gamma subunit rotation physically pushes subunits through cycle
•
12 H+ (12 subunits) = 3 ATP (1 full rotation of gamma subunit)!
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Rotation of the F0γ subunit pushes the F1 Β subunits through their 3-state cycle
•
Uses water flow downhill to rotate magnets in generator to produce
current!
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ATP synthase is the world’s smallest turbine generator
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Max Speed: 130 revolutions/sec!!
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Bacteria from hot springs allowed for stable ATP synthase purification
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The movement of ATP synthase has been directly visualized using reverse reaction
of gamma subunit with ATP hydrolysis and reverse proton gradient
•
The F1 subunits exist in 3 discrete conformations
Each ATP needs 1 H+ for transport purposes!
•
Same for flow of ADP back into matrix
○
This electron does not come back through the ATP synthase!
▪
One ATP burns an extra proton in transport!
▪
Phosphate transporter takes phosphate in, transfers OH- out,
which will then form water using proton from the ETC
○
Free energy to be gained by transfer down [ ] gradient into
intermembrane space
•
An African herbal remedy (Atractyloside) is an inhibitor of the ATP/ADP
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ATP escapes the mitochondrial matrix via an ATP/ADP antiporter
Lecture 9: ATP Synthesis
January 31, 2018
9:40 AM
Section 1 Page 1
Document Summary
Atp synthase harnesses the protonmotive force to make atp. Composed of two fragments: f1 (hexameric head and shaft component) and f0 (intermembrane components) Head made of 3 alpha 3 beta subunits, where atp is synthesized. Contains proton half channels, contains pka- regulated residues where protons flow through. Enter 1st helf channel --> around rotating c-ring --> second half channel. Rotation of c ring causes simultaneous atp synthesis. Coupling allowed by gamma subunit which rotates with c ring, drives conformational changes in a/b subunits. The f0 subunit c ring rotates as protons pass through it. Arg residue with net + charge and glu residues that carry negative charge that interacts with it. Proton enters and begins to interact with - residue, dislodges arg (favourable due to concentration gradient, different structures of channels altering respective pkas) Arg swings onto different (-) charge on adjacent c-ring subunit, dislodges proton in 2nd half channel into matrix.
