molecular docking and qsar analysis: a combined approach applied to ftase
DESCRIPTION
Università degli Studi di Milano. Molecular docking and QSAR analysis: a combined approach applied to FTase inhibitors and a 1a -AR antagonists. Giulio Vistoli, Alessandro Pedretti. The Farnesyltransferase. - PowerPoint PPT PresentationTRANSCRIPT
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Molecular docking and QSAR analysis:a combined approach applied to FTase
inhibitors and 1a-AR antagonists
Università degli Studi di Milano
Giulio Vistoli, Alessandro Pedretti
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The Farnesyltransferase
•The Farnesyltransferase (FTase) catalyzes the transfer of a farnesyl group from farnesyl diphosphate (FPP) to a specific cysteine residue of a substrate protein through covalent attachment.
•This post-translational modification is believed to be involved in membrane association due to the enhanced hydrophobicity of the protein upon farnesylation.
•This modification process has been identified in the Ras proteins that play a crucial role in the signal transduction pathway that leads to cell division.
•Preventing the farnesylation process may be a possible approach for anti-cancer chemotherapy.
•Knowledge about the active site environment of FTase is important in designing of new potent enzyme inhibitors.
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Pattern Recognition
•The FTase recognizes the CA1A2X at the C-terminal position of the RAS protein:
CA1A2X
•C is the cysteine residue to which the prenyl group is attached;
•A1 and A2 are aliphatic amino acids;
•X is the carboxyl terminus specifying which prenyl group is attached (geranylgeranyl or farnesyl group).
•The enzyme catalyzes also the transfer of the farnesyl group on the partial tetrapeptide isolated from the main chain.
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RAS Protein Posttranslational Modification
NH
SH
O
Val-Ile-Met-OH
1. Endoprotease2. Methyltransferase
FTase
NH
S
O
OMe
+O
PO
PO
O O
O O- --
Palmitoylzation andmembrane localization
NH
S
O
Val-Ile-Met-OH
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The Farnesyltransferase Crystals Structure
•The crystal structure of rat FTase was resolved at 2.25 Å resolution.
• This protein is an heterodimer consisting of 48 kD () and 46 kD () subunits.
•The secondary structure of both and subunits appears largely composed of -helices.
•A single zinc ion, involved in catalysis, is located at junction between the hydrophilic surface of subunit and thehydrophobic deep cleft of subunit.
•The zinc is coordinated by three subunit residues and one water molecule.
subunit
subunit
Zn
Watermolecules
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Classification of the FTase Ligands
FTase
Peptidomimetics
FPP mimetics
Natural comp.
InhibitorsActivatorsSubstrates
Transition state analogues
Catalyticmechanism
Inhibitionmechanism
Pharmacophore
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Computational Methods
•Construction of the ligands
The conformational analysis was performed using high temperature (2000 K) molecular dynamics (500 ps), which is able to span the conformational space of flexible molecules. The best structure obtained was finally optimized by MOPAC 6.0.
•Docking analysis
It was performed using BioDock: a software for automated docking of ligands to biomacromolecules, based on a stochastic approach.
•FTase crystal structure refinement
The structure was minimized using both steepest descent algorithm until RMS = 0.5 and conjugated gradients until RMS = 0.01, keeping backbone constrained to preserve the experimental structure. The water molecules are preserved in all simulations.
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BioDock
Randomrototranslation of the ligand
Complexevaluation
The complex is bad
Newcomplex
Ligand
Receptor
Clusteranalysis
End ofdocking
NO
Cluster 1
Cluster 2
Cluster 3
Cluster n
YES
Stop
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CA1A2X Peptides
H3NNH
NH
NH
O
O
O
O
OSH
S
-+
Cys-Val-Ile-Met (CVIM)
H3N NH
SH
O
O
NH
O
NH
OH
O
O
+
Cys-Val-Leu-Ser (CVLS)
H3NNH
NH
NH
O
O
O
O
OSH
S
NH
-
Cys-Val-Trp-Met (CVWM)
H3NNH
NH
NH
O
O
O
O
OSH
S
-
Cys-Val-Phe-Met (CVFM)
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CVIM Peptide Conformations
CVIM - extendeddist. = 11.6 Å
CVIM - foldeddist. = 8.3 Å
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CVIM Conformational Analysis
Activator
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CVWM Conformational Analysis
Inhibitor
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Conformational Analysis Results
From these results, we can suppose a hypothetical catalytic mechanism consisting of two steps:
Conformationalinterconversion
Recognition Extended conformation
ActivationFolded conformation
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Natural Inhibitors(1)
OO
O OHO
OH
MeO
OO
OO
OH
COOH
OH
COOH
COOH
O
FusidienolIC50 = 300 nM
Zaragozic acidIC50 = 12 nM
OO
CH3
CH3
H
HCH3
H
O
OO
CH2
CH3
H
H
CH3 CH3
O OH
ArtemidolideIC50 = 360 nM
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Natural Inhibitors(2)
O
H
CH3
HOCH3
CH3
CH3
O
CH3
CH3
CH3
COO-OH
R
Andrastatin A (R =CHO) IC50 = 24.9 MAndrastatin B (R =CH2OH) IC50 = 47.1 MAndrastatin C (R =CH3) IC50 = 13.3 M
CH3
O CH3
CH3
CH3
CH3
CH3
HOOC
Des-AIC50 = 0.9 M
CH3
O
CH3
CH3
CH3
CH3
HOOC
HOOC
Des-BIC50 = 0.19 M
COOH
HOOC
Z-Schizostatin IC50 = 300 M
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FTase - Fusidienol Complex
Beta subunit
Alpha subunit
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Site Selectivity
Compound Type VO%CVLS VO%FPP
CVLS - 100 0
FPP - 0 100
Fusidienol N.S. 15,7 17,7
Zaragozic acid N.S. 41,7 41,3
Andrastatin A CVLS 43,3 6,1
Andrastatin B CVLS 41 11,9
Andrastatin C CVLS 44 6
Arteminolide CVLS 47,3 26,9
Clav-A 1S,2R CVLS 54,7 4,4
Clav-B 1S,2R FPP 26,5 39.3
Schizostatin Z FPP 10 36.6
Schizostatin E FPP 7.1 27.8
Inhibition mechanism (Type): N.S. (not-selective), CVLS (peptidomimetic), FPP (FPPmimetic).
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Classification of the Natural Inhibitors
Natural inhibitors
FPP-mimetic VCVLS VFPP
Peptidomimetic VCVLS VFPP
lipole
Zn++ shielding VCVLS VFPP
Non specific pos. VCVLS VFPP
volume
Zaragozic Acid Fusidienol
Artemidolide Schizostatin
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The Lipole
The lipole is calculated as sum of local values of logP, like dipolar momentum:
i
iirL
Where:
ri is the distance between atom i and the geometric center of the molecule;
li is the atomic value of the lipophilicity of atom i.
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Lipole and Site Selectivity
Compound Type Lipole LogP
CVLS - 2.2 -0.5
FPP - - -
Fusidienol N.S. 1.4 1.8
Zaragozic acid N.S. 0.8 2.0
Andrastatin A CVLS 2.2 1.7
Andrastatin B CVLS 2.2 1.6
Andrastatin C CVLS 2.5 2.7
Arteminolide CVLS 2.5 1.8
Clav-A 1S,2R CVLS 2.1 6.0
Clav-B 1S,2R FPP 4.3 4.2
Schizostatin Z FPP 6.7 1.4
Schizostatin E FPP 6.0 1.3
Lipole < 2.0Non-specific inhibitors
2.0 < Lipole < 4.0Peptidomimetics
Lipole > 4.0FPP-mimetics
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VEGA and the Lipole Calculation
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File Conversion
VEGA Main Features
VISUALIZATION
Surface Mapping Trajectory Analysis
DataInterchange
Dockinganalysis
Force fieldattribution
ShapeAnalysis
WebPublishing
PropertyCalculation
DynamicAnimation
TimeProfiling
Flexibilityanalysis
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Pharmacophoric Model
O H
Tyr-361
OH
Tyr-300
NH NH 2
N H 2+
NHNH 2
N H 2+
A rg -291
A rg -202
NNH
NNH
H is-201 H is-248
NH 3 NH 3
++
Lys-164 Lys-356
Zn++
E lectronrich zone
A m id icgroups
Arom aticfunctions
P H A R M A C O P H O R ICG R O U P S
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Acknowledgments
Bernard Testa
Luigi Villa
Anna Maria Villa
Lidia Perri
Eleonora Vocaturo
Antonio Boccardi
http://users.unimi.it/~ddl