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ATP Synthase: What Does It Take to ATP Synthase: What Does It Take to Make a Rotary Enzyme?Make a Rotary Enzyme?

Stan DunnStan DunnDepartment of BiochemistryDepartment of Biochemistry

Schulich School of Medicine & DentistrySchulich School of Medicine & Dentistry24 April 201324 April 2013

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ATP (ATP (AAdenosine denosine TTririPPhosphate) Is the Primary hosphate) Is the Primary Biological “Energy Currency”Biological “Energy Currency”

Cell maintenance, protein and nucleic acid biosynthesis

Active transport

Muscle contraction

Food

CO2 and H2O

Oxidative phosphorylation

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The Mechanism of Oxidative PhosphorylationThe Mechanism of Oxidative Phosphorylation

Respiratory Complexes I, III, IVATP synthase,aka Complex V

Respiratory complexes use the energy released during the oxidation of food to drive H+ ions across the inner mitochondrial membrane, producing an electrochemical H+ gradient containing potential energy; ATP synthase allows the H+ to return, using the released energy to convert ADP + Pi into ATP

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F-ATP Synthase: two motors sharing one driveshaft/rotorF-ATP Synthase: two motors sharing one driveshaft/rotor

F1

• peripheral

•• ATP synthesis/hydrolysis•chemical rotary motor

ADP + Pi

ATP

The stator:

33ab2

The stator stalk: b2

Fo

• integral•ab2c10

•H+ conduction•electrical rotary motor

C10

b2

aH+

H+

The rotor: c10

A common driveshaft

Image courtesy of Achim Weber

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Analysis of Analysis of E. coli bE. coli bsolsol

• Dimer• Highly extended, not globular • Binds to F1 sector, through subunit• Highly -helical• Sequence shows heptad repeat pattern

So we expected bsol to form a left-handed coiled coil

1 23 53 122 156

Membrane Tether Dimerization F1-Binding

bsol

Properties of bsol

Left-handed coiled coil

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Arrangement of helices in dimerization domainArrangement of helices in dimerization domainDisulfide formation between introduced cysteine residuesDisulfide formation between introduced cysteine residues

Our conclusion: b2 forms ”an atypical coiled coil”

Heptad: b c d e f g a b c dResidue: 59 60 61 62 63 64 65 66 67 68 WT res: A S A T D Q L K K A

Ala to Cys mutation changes the side chain from –CH3 to –CH2SH

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““Troubles are good for you.”Troubles are good for you.”

--Efraim Racker, Cornell UniversityEfraim Racker, Cornell University

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““Work hard, don’t have fun, Work hard, don’t have fun, and save your money for your and save your money for your

old age.”old age.”

--Leon Heppel, Cornell UniversityLeon Heppel, Cornell University

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The dimerization domain of The dimerization domain of bb

•Dimer in solution, but monomer in crystal (crystallization from MPD/isopropanol/water)

•Panel A shows hydrophobic face with alanines in orange, branched aliphatics in green.

•Panel B highlights alanines along the face

•Panel C shows a model dimerized about this face: this will produce a right-handed coiled coil

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Selective disulfide bond formation between Selective disulfide bond formation between aa and and hh positionspositions

Observation: preferential disulfide formation between an (a) position from one helix and the (h) from the adjacent helix.

This result implies that (a) & (h) positions are at the helix-helix interface … but how can 79 link to 72 and 83?

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A68( )h

A72( )a

A79( )h

A79( )h

A83( )a

A72( )a

bC

i

i i

i ii

b N

bC bN

i 68(h) x 72(a)ii 72(a) x 79(h)iii 79(h) x 83(a)iv 83(a) x 90(h)

Offset right-handed coiled coil model of Offset right-handed coiled coil model of bb

These disulfide-linked forms had shapes and stabilities characteristic of native proteins

They also interacted strongly with F1-ATPase

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Structure of Structure of Thermus thermophilusThermus thermophilus EG EG

Danielle Stock and co-workers, NSMB 2010

alanine zipper

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Functional relevance of right-handedness of Functional relevance of right-handedness of bb22: structural stabilization to torque on stator: structural stabilization to torque on stator

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AcknowledgmentsAcknowledgments

Yumin Bi

Paul Del Rizzo

Derek McLachlin Greg

Gloor

Brian Shilton

Graduate studentsArdy GoliaeiKristi WoodDan CiprianoLee-Ann BriereMatt Revington

UndergraduatesCarla Busnello

Karen DunkerleyNancy WangKevin Talbott

Chelsea BotsfordStahs Pripotnev

Western James ChoyGary ShawGreg Gloor

Eric BallLindi Wahl

Mike Strong

CanadaQuim Madrenas

Liz Meiering

InternationalBrian Cain

Stephan WilkensWolfgang JungeMichael Bӧrsch

Gabriele Deckers-Hebestreit

Paola TurinaMasamitsu Futai