It is a collection of membrane-embedded proteins and organic molecules, most of them organized into four large complexes labeled I to IV. The resulting proton gradient is used by the ATP synthase complex for ATP formation. ATP synthesis is driven by the return of protons to the matrix through an integral membrane protein complex known variously as ATP synthase.

1. STRUCTURE OF ATPase
COMPLEX-V
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2. INTRODUCTION
 During cellular respiration, organic compounds are oxidized to generate
usable chemical energy in the form of ATP.
 The respiratory electron transport chain (ETC) of mitochondria is at the
center of this process.
 The respiratory electron transport chain (ETC) couples electron transfer
from organic substrates onto molecular oxygen with proton translocation
across the inner mitochondrial membrane.
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3.  It is a collection of membrane-embedded proteins and organic
molecules, most of them organized into four large complexes
labeled I to IV.
 The resulting proton gradient is used by the ATP synthase
complex for ATP formation.
 ATP synthesis is driven by the return of protons to the matrix
through an integral membrane protein complex known variously
as ATP synthase.
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4.  In 1960 the American scientist Efraim Racker and co-workers isolated,
from mitochondria, the enzyme “F0 F1 ATPase” which we now call ATP
synthase.
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5. ATP SYNTHASE
 This is one of the most conserved proteins in Bacteria, Plants and
Mammals.
 This enzyme is the smallest known biological nanomotor and plays a
crucial role in ATP generation.
 The enzymes are essentially the same in structure and function as
those from mitochondria of animals, plants and fungi, and the
chloroplasts of plants.
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6. TYPES OF ATPase
 There are three classes of ATPases, which differ in structure and the type
of ion that they transport;
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7. ATPase (complex v) IN PLANTS
 ATP synthase is a protein that is responsible for the generation of
ATP through phosphorylation of ADP by using electrochemical
energy generated by proton gradient across the inner membrane of
mitochondria.
 These are protein clusters.
 In plant cells, ATP synthase complex resides in a inner mitochondrial
membrane and thylakoid membrane. ADP phosphorylation occurs in
this complex, resulting in the synthesis of ATP molecules during
photosynthesis.
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8. FUNCTION OF ATP SYNTHASE
 The enzyme ATP synthase has diverse functions.
 ATP synthase function includes: Synthesizing ATP molecules to provide
organisms with an abundant high-energy source. It acts as the
powerhouse of the cell by synthesizing ATP.
 It can also operate in the reverse direction, hydrolysing ATP and
pumping protons under certain conditions.
 It pumps protons outside during hydrolytic activity, whereas the protons
may pass inside through the ATPase during synthetic activity.
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9. STRUCTURE OF ATP SYNTHASE
 ATP synthase is a large mushroom-
shaped asymmetric protein complex.
 The mitochondrial ATP synthase is a
multi-subunit protein complex having an
approximate molecular weight of 550 kDa.
 It has two subunits,
1. F0 unit (rotational)
2. F1 unit (catalytic)
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10. F1 COMPONENT
 F1 (factor 1) component projects into the matrix from the inner membrane.
 It is hydrophilic region.
 F1 unit functions as the active centre.
 John Walker deduced the high-resolution structure of the F1 part of ATP synthase enzyme
and jointly owned the Nobel Prize with Paul Boyer in 1997 in chemistry.
 Mitochondrial F1 has nine subunits of five different types,
1. Three α subunits
2. Three β subunits
3. Single γ subunit
4. Single δ subunit
5. Single ε subunit
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11. 1. Alpha (α) subunit :
promotes activity
of beta.
2. Beta (β) subunits :
Catalytic site for ATP
synthesis.
3. Gamma (γ) subunit :
Forms the central stalk
connects F0 with F1
4. Delta (δ) subunit :
Holds a, β hexamer in
a fixed position
5. Epsilon (ε) subunit :
Attach γ subunit with
C10 ring
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12. 12

13. ALPHA AND BETA SUBUNIT
 In F-ATPases, there are three copies
each of the alpha and beta subunits that
form the catalytic core of the F1 complex,
while the remaining F1 subunits (gamma,
delta, epsilon) form part of the stalks.
 There is a substrate-binding site on each
of the alpha and beta subunits, those on
the beta subunits being catalytic, while
those on the alpha subunits are
regulatory.
 The alpha and beta subunits form a
cylinder that is attached to the central
stalk.
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14.  The beta subunits undergo a sequence of conformational changes
leading to the formation of ATP from ADP, which are induced by the
rotation of the gamma subunit, itself is driven by the movement of protons
through the F0 complex C subunit.
 The structure of the alpha and beta subunits is almost identical. Each
subunit consists of a N-terminal β-barrel, a central domain containing the
nucleotide-binding site and a C-terminal α bundle domain of 7 and 6
helices, respectively, in the alpha and beta subunits .
 Each of the three β subunits has one catalytic site for ATP synthesis.
 The knob like portion of F1 is a flattened sphere, 8 nm high and 10 nm
across, consisting of alternating α and β subunits arranged like the
sections of an orange.
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15.  The αlpha and β-subunits arranged in an alternating manner
(αβαβαβ) to form a hexameric ring with the γ-subunit at its
center.
 There are six nucleotide-binding sites at the interfaces
between the α- and β-subunits.
 Three of the nucleotide-binding sites are catalytically active,
whereas the other three nucleotide-binding sites are not
catalytically active.
 The three catalytically active sites are mainly encompassed
by the β-subunits and therefore are termed the β-subunit
sites.
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16.  The ATPase F1 complex gamma subunit forms the
central shaft that connects the Fo rotary motor to the
F1 catalytic core.
 The gamma subunit functions as a rotary motor
inside the cylinder formed by the alpha(3)beta(3)
subunits in the F1 complex.
 The best-conserved region of the gamma subunit is
its C terminus, which seems to be essential for
assembly and catalysis.
 The δ and ε subunits of F1, form a leg -and-foot that
projects from the bottom side of F1 and stands firmly
on the ring of c subunits.
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17. F0 COMPONENT
 The second component of ATP synthase.
 It is the Hydrophobic region.
 It spans the inner mitochondrial membrane.
 F0 unit is composed of four polypeptide chains.
 All the polypeptides of the F0 unit are of same kind.
 F0 is a specific protein factor which when added to the F1 results in the inhibition
of the ATP synthase activity by Oligomycin. Hence F0 is also called oligomycin
sensitivity conferring factor or OSCF. There is a channel through F0 that
specifically translocates protons on both sides.
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18.  The Fo complex making up the proton pore is
composed of three subunits, a, b, and c.
a subunit – 1
b subunit – 2
c subunit – 10 to 12
 Subunit a: forms proton channel
 Subunit b: forms peripheral stalk connects F0 with
F1.
 Subunit c is a small, very hydrophobic
polypeptide, consisting almost entirely of two
trans-membrane helices, with a small loop
extending from the matrix side of the membrane.
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19.  Biochemical and mutational experiments have shown that the a
and c subunits contain functional groups that are necessary for
proton translocation through the membrane.
 The a & b subunits align the exterior of the multimeric c subunits.
 The cavity in between a and c subunits providing the pathway for
protons.
 Protonation and deprotonation in this interface is thought to
cause rotation of the c ring thereby rotating the gamma subunit.
 The synthesis of ATP requires 120 degrees.
 In certain some synthases with a 9 c subunit ring require 3 proton
translocations.
 In other synthases with a 10 c subunit ring require 4 proton
translocations
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20.  The Fo portion of the ATP synthase comprises the proton turbine as well
as the base of the stator.
 The core of Fo is composed of an oligomer of the c-subunits, which
contain an essential carboxylate from the side chain of either a glutamate
or aspartate residue. The side chain carboxyl acts as the proton donor
and acceptor in proton translocation pathway.
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21. Rotor
 The C9-12 complex along with the ƴ and ε
constitute the moving unit, i.e. rotor. It undergoes
rotational motion, as the protons or H+ ions move
across the thylakoid membrane.
 Due to the rotary mechanism, ATP synthase is also
termed as molecular machine.
Stator
 The B2 and a subunit along with the α3 β3 δ
complex, makes up the stationary unit, i.e. stator.
The stator is also referred to as the peripheral or
extrinsic stalk.
 The stator functions to hold F1 fixed to allow
rotation of the rotor within the core of F1. The stator
provides a structural support and is not involved
directly in the catalytic reaction.
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22. Central stalk
 It is Considered part of the Fo rotor, it connects the Fo and F1 motors
together.
 The central stalk of mitochondrial ATP synthase consists of subunits γ, δ,
and ε, and along with the membraneous subunit c oligomer constitutes
the rotor domain of the enzyme.
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24. Inhibitor of Mitochondrial ATP Synthase
ATP synthesis in chloroplast and mitochondria can be inhibited by
the destruction of ATP synthase in mitochondria, there are some
examples of such inhibitor of mitochondrial ATP synthase
1. Aurovertin- It inhibits the F1 domain of the ATP synthase.Each β
subunit contains one aurovertin binding site .
2. Oligomycin – It inhibits the Fo domain of the enzyme.Oligomycin
is a competitive inhibitor
3. Ventriuricidin- It inhibits the Fo domain of the chloroplast ATP
synthase
4. DCCD- It blocks the proton flow through the form of mitochondrial
and chloroplast ATP synthase.
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25. REFERENCE
 Hopkins, G., William. (1995). Introduction To Plant Physiology. John Wiley and Sons, Inc.
 Ghosh, A.K., Mukherji, S. (1996). Plant Physiology. New Central Book Agency Pvt. Itd.
 Verma, V (2007). Textbook of Plant Physiology (4th ed). Thomson Asia Pvt.ltd,
Singapore.
 https://study.com/academy/lesson/atp-synthase-definition-structure-function.html
 https://microbiochem.weebly.com/structure-and-mechanism-of-atp-synthase.html
 https://biologyreader.com/atp-synthase-in-photosynthesis.html
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