alessandro agostini biophysics group
TRANSCRIPT
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Marco Bortolus
Biophysics
group
Alessandro Agostini
CW/Pulse X/Q Band EPR
Department of Biology, University of Padova
Paola Costantini
Davide Doni
Department of Chemical Sciences, University of Padova
€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€
CARIPARO Foundation (Starting Grant 2015-2019 Carbonera/Bortolus)
Donatella Carbonera
Elisabetta Bergantino
Department of Biology, University of Padova
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Metodologie che lo studente può imparare
Metodologie di biologia molecolare (PCR, clonaggi, mutagenesi)
Metodologie biochimiche per la purificazione di proteine ricombinanti
espresse in diversi sistemi eterologhi (elettroforesi mono- e bidimensionali,
cromatografie di affinità, a scambio ionico e gel filtrazione, western blot) e per il
loro labelling con probes fluorescenti e di Spin elettronico
Metodologie Spettroscopiche per la caratterizzazione strutturale di proteine
in soluzione principalmente FRET, CD e EPR (electron paramagnetic
resonance)
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FLUORESCENT LABELLING
SPIN LABELLING
Labelling proteins
The site directed spin labelling
(SDSL) Technique
•
•
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SPIN LABELING
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Immobilized
F
L
U
I
D
I
T
Y
M
O
B
I
L
I
T
Y
Mobile
Spectral Width: Mobility parameter
Spin labeling coupled to EPR techniques
-
B
dip
Dipolar interaction
4-pulse DEER
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Frataxin, a protein involved in the iron-sulphur clusters synthesis
Assemblaggio dei centri ferro-zolfo
Frataxin
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Frataxin, a protein involved in the iron-sulphur clusters synthesis
Frataxin is a small acidic protein, highly conserved in most organisms from bacteria to
mammalians, which so far has been supposed to have a role in the iron-sulphur cluster
biosynthesis.
A low expression level of this protein is associated to the neurodegenerative disease
Friedreich’s ataxia (FRDA), whose main biochemical feature is a large depletion of proteins
relying on iron-sulphur clusters for function
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Frataxina e atassia di Friedriech
Struttura di
frataxina (FXN)
Paziente con
sindrome di Friedriech
1
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WT
FXN
D122Y
FXN
Fe(III
)
Fe(II)
Tecniche
spettroscopiche:
•Fluorescenza
•Dicroismo circolare
•Dynamic light
scattering
•SDSL-EPR
Differenze e
analogie nella
risposta per
investigare la
funzione
fisiologica
4
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SDSL-EPR dei mutanti FXN-Cys
I diversi siti marcati della proteina presentano una diversa
mobilità.
>100 ns
<100 ps
Mo
bilità
10
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Fe(III): effetto sugli spettri EPR
Fe(III)
Fe(III)
Tutti i siti marcati si immobilizzano in presenza di
Fe(III).
0 eq. Fe(III)
10 eq. Fe(III)
11
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The FXN point mutants D122Y, G130V, N146K, and W155R are all associated with an FRDA phenotype.
We have already investigated them by NMR spectroscopy (submitted), finding perturbation of the NMR
spectrum in each mutant when iron and ISU were subsequently added.
T1. In vitro experiments using purified recombinant proteins /WT and
mutants) to study the conformational effects induced by Fe and the
putative interface regions between FXN and ISU by FRET and EPR.
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Cameleon (protein): sensori del Calcio
(M13: from skeletal muscle myosin light- chain
kinase (MLCK) .
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Immobilized
F
L
U
I
D
I
T
Y
M
O
B
I
L
I
T
Y
Mobile
Spectral Width: Mobility parameter
Spin labeling coupled to EPR techniques
-
B
dip
Dipolar interaction
4-pulse DEER
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Photoexcited triplet state – nitroxide distanceT
Porphyrin Triplet State as a Potential Spin Label for Nanometer Distance Measurements by PELDOR
SpectroscopyMarilena Di Valentin; Marco Albertini; Enrico Zurlo; Marina Gobbo; Donatella Carbonera; J. Am. Chem. Soc. 2014, 136, 6582-6585.
bis-labeled peptide TPP-(Ala-Aib)4-Ala-TOAC-Ala-(Aib-Ala)2-OH.
300 320 340 360 380
B0 (mT)
A
E
PUMP (NO.)
OBSERVER (3TPP)
PELDOR Pulse sequence
TTP-NO labeled peptides
ωObs
ωPump
TPP
TOAC
Aib
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-1 0 1 2 3 4 5 6 7 8
0.0
0.5
1.0
1.5
2.0
2.5
3.0
V(t
) /V
(0)
t [s]
TPP-(Ala-Aib)12-Ala-(Aib-Ala)6-Ala-Aib-Ala-Aib-Ala-Aib-Ala-Aib-Ala-Ala-TOAC-Ala-Aib-Ala-OH
TPP-(Ala-Aib)2-Ala-Ala-TOAC-(Ala-Aib)4-Ala-OH
TPP-(Ala-Aib)2-Ala-Aib-Ala-TOAC-(Ala-Aib)3-Ala-OH
TPP-(Ala-Aib)2-Ala-Aib-Ala-Aib-Ala-TOAC-(Ala-Aib)2-Ala-OH
TPP-(Ala-Aib)3 -Ala-Aib-Ala-(Ala-Aib)2-Ala-TOAC-Ala-Aib-Ala-OH
TPP-(Ala-Aib)2-Ala-Aib-Ala-Aib-Ala-(Ala-Aib)4-Ala-TOAC-Ala-Aib-Ala-OH
TPP-(Ala-Aib)6-Ala-Aib-Ala-Aib-Ala-Aib-Ala-Aib-Ala-Ala-TOAC-Ala-Aib-Ala-OH
TPP-(Ala-Aib)6-Ala-(Aib-Ala)6-Ala-(Ala-Aib)2-Ala-Aib-Ala-Aib-Ala-TOAC-Ala-Aib-Ala-OH
18 Å
21 Å
23 Å
31 Å
38 Å
43 Å
62 Å
81 Å
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
1 2 3 4 5 6 71
2
3
4
5
6
7
rPELDOR
= -0.02 + 0.96 rMODEL
r PEL
DO
R [
nm
]
rMODEL
[nm]
(1)
(2)
(3)(4)
(5) (6)
(7)
PELDOR
Correlation between structural models and
PELDOR derived distances
T
Photoexcited triplet state – nitroxide distance
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Distance measurements in peridinin-chlorophyll a-protein by light-induced PELDOR
spectroscopy. Analysis of triplet state localizationBiochimica et Biophysica Acta (BBA) – Bioenergetics 2016 1857, 1909-1916
-20 -10 0 10 20
Frequency (MHz)
-20 0 20
Frequency (MHz)
-20 0 20
Frequency (MHz)
-20 0 20
Frequency (MHz)
Per
4
Per2
Per3
Per1
0.0 0.4 0.8 1.2
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Nor
mal
ized
Inte
nsity
Time (s)
0.0 0.4 0.8 1.2
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Nor
mal
ized
Inte
nsity
Time (s)
0.0 0.4 0.8 1.2
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Nor
mal
ized
Inte
nsity
Time (s)
0.0 0.4 0.8 1.2
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Nor
mal
ized
Inte
nsity
Time (s)
HS
|
protein
N-RFPCP (N-ter refolded PCP)
MTSSL
Site-directed Spin-labelling (SDSL)
260 280 300 320 340 360 380 400
pump
observer
Magnetic field [mT]
TPer4-NO1 <20>ÅTPer4-NO2 <40>Å
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Alignment of the CaM-binding peptides used in this study, as well as smMLCKp (19).
Richard D. Brokx et al. J. Biol. Chem. 2001;276:14083-14091
The American Society for Biochemistry and Molecular Biology, Inc.
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Distanza Cys-Tyr138 varia poco sempre intorno ai 35 A
Distanza Cys-Tyr99 varia da 41 a 49 A
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Distanza Cys-Phe92 varia varia da 29 a 44 A
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Mechanical incorporation
Labeled proteins
in vivo experiments
Unnatural aminoacids