BL5203: Molecular Recognition & Interaction Lecture 5: Drug Design Methods Ligand -Protein Docking (part II) Prof. Chen Yu Zong Tel: 6874-6877 Email: [email protected] http://xin.cz3.nus.edu.sg Room 07-24, level 7, SOC1, National University of Singapore. Conformational Ensembles Docking. - PowerPoint PPT Presentation
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1. Generating an orientation of a ligand in a binding site may be separated from calculating a conformation of the ligand in that particular orientation.
2. Multiple conformations of a given ligand usually have some portion in common (internally rigid atoms such as ring systems), and therefore, contain redundancies.
• Conformational ensembles are generated by overlaying all conformations of a given molecule onto its largest rigid fragment.
• Only atoms within this largest rigid fragment are used during the distance matching step. The RT matrix is defined.
• Each of the conformers is oriented into the site and scored. The score measures steric and electrostatic complementarity.
• One matching steps - all the conformers are docked and scored in the selected orientation.
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Overview of the Ligand Ensemble MethodOverview of the Ligand Ensemble Method
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Advantages of Conformational Ensemble Advantages of Conformational Ensemble DockingDocking
Speed increase due to:
• One matching step for all of the conformers.
• The largest rigid fragment usually has fewer atoms (less potential matches are examined).
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Disadvantages of Conformational Disadvantages of Conformational Ensemble DockingEnsemble Docking
• Loss of information when the orientations are guided only by a subset of the atoms in molecule. Orientations may be missed because potential distance matches from non-rigid portions of the molecule are not considered.
• The ensemble method will fail for ligands that lack internally rigid atoms.
• The use of chemical matching and critical clusters is limited.
• Appropriate spatial disposition of a small number of functional groups in a molecule is sufficient for achieving a desired biological effect.
• The ensemble formation will be guided by these functional groups.
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3-D Representation of a Protein Binding Site3-D Representation of a Protein Binding Site
5.2
4.2-4.7
6.7
4.8
5.1-7.1 Distances betweenbinding groupsin Angstroms and the type of interactionis searchable
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Pharmacophore FingerprintPharmacophore Fingerprint• Pharmacophore fingerprint - a set of pharmacophore
features and their relative position.• Typical pharmacophore features:
– Hydrogen-bond donors and acceptors– Positive and negative ionizable atoms/groups– Hydrophobes and ring centroids
• Implemented in DOCK 4.0.1– Hydrogen-bond donors– Hydrogen-bond acceptors– Dual hydrogen-bond donor and acceptor – 5 or 6 membered ring centroids
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Notes on Pharmacophore FingerprintNotes on Pharmacophore Fingerprint
• Each conformer has pharmacophore fingerprint.
• Different conformers of the same molecule can have identical pharmacophore fingerprints.
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Pharmacophore DOCKPharmacophore DOCK
Prepare target structure
Generate a set ofchemically labeled site
points
Read a 3D pharmacophorefrom the database
Compare distances betweenpharmacophore points andsite points to determine an
orientation matrix
Match?
NoYes
Orientationstries >MAX
Orientationstries >MAX
No No
Yes Yes
Use the transformation matrix todock all conformers associated with
the pharmacophore
Score allconformers
Save the best scoringconformer for each molecule
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Advantages of Pharmacophore-based DockingAdvantages of Pharmacophore-based Docking
• Rapid elimination of ligands containing functional groups which would interfere with binding.
• Speed increase over docking of individual molecules.
• More information pertaining to the entire molecule is retained (no rigid portions).
• Chemical matching and critical clusters are encouraged.
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Speed Comparison Between Ensemble Speed Comparison Between Ensemble and Pharmacophore-based Docking.and Pharmacophore-based Docking.
Pharmacophore-based advantage:
• Reduced number of ligand points considered during distance matching.
Ensemble docking advantage:
• The average number of conformers per molecule is higher than the average number of conformers per fingerprint. The one step matching speed reduction is slightly higher.
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Speed Reduction Cont.Speed Reduction Cont.
• Ensemble docking:the average number of conformers per molecule is 297.
• Pharmacophore-based:50-100 conformers per pharmacophore
Rigid Fragment Conformer 1 Conformer 2 Confomer 297
1. Extract 3D pharmacophore from the first molecule of a cluster
2. Use it to perform a rigid 3D UNITY search of the rest of that cluster to find matches
3. Save the pharmacophore querywith the associated molecules
4. Process until all molecules are
associated with a pharmacophore
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Site Points GenerationSite Points Generation
• Chemically labeled site point are generated in an automated fashion using the script MCSS2SPTS .
• The script runs a series of MCSS (Multiple Copy Simultaneous Searches) calculations.
• MCSS – methodology for finding energetically favorable positions and orientations of small functional group in a binding site.
• Uses CHARMM potential energy function to determine the preferred locations or potential energy minima simultaneously for thousands of copies of a given chemical group.
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Limitations of Pharmacophore-based Limitations of Pharmacophore-based SearchingSearching
• A limited subset of key interactions (typically 4-6) which must be extracted from the target site with dozens of potential interactions.
• Complex queries are extremely slow.• The majority of the information contained in the target
structure is not considered during the search. There is no scoring function beyond the binary (match/no match). Any steric or electronic constraints imposed by the target, but not defined by the target are ignored.
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INVDOCK StrategyINVDOCK StrategyExisting M ethods:
G iven a Protein,F ind Puta tive B inding L iga nds
From a C hem ica l D a ta ba se
S uccess fu l ly D ocked C om poundsas Puta tive L igands
Protein
C om pound D a ta ba seC om pound 1
...C om pound n
N ew M ethod:G iven a L iga nd,
F ind Puta tive Protein T a rgetsFrom a Protein D a ta ba se
S uccess ful ly D ocked Prote insas Puta tive T arge ts
S tep 1 : V ec tor-based dock ing of a l igand to a cavityS tep 2 : L im ited conform ation optim iza tion on the l igand and s ide cha in of b iom oleculeS tep 3 : E nergy m inim iza tion for a l l a tom in the b inding s i teS tep 4 : D ock ing eva lua tion by m olecula r m echanics energy func tions and com parison w ith other l igands
P ro te in fun c tio n , P ro teo m ics , L ig an d tran sp o rt, M e tab o lism
Th erap eutic Ta rg e ts , S id e -E ffec ts , M e tab o lism , To x ic ityFunction in Pathw ays
P o ten tia l Ap p lica tio n s :\|/
S uccess fu l ly D ocked Prote ins and Nuc le ic A c idsas Puta tive T arge ts of a L igand
|\|/
A utom ated Process to inverse ly dock the L ignad to each entry ina Buil t-In B iom olecula r C avity D a tabase (10 ,000 Prote in and Nuc le ic A c id E ntr ies )
\|/
L igand\|/
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INVDOCK Test on Drug Target PredictionINVDOCK Test on Drug Target Prediction Anticancer Drug Tamoxifen
PDB Id Protein Experimental Findings 1a25 Protein Kinase C Secondary Target1a52 Estrogen Receptor Drug Target1bhs 17beta Hydroxysteroid dehydragenase Inhibitor1bld Basic Fibroblast Growth Factor Inhibitor1cpt Cytochrome P450-TERP Metabolism1dmo Calmodulin Secondary Target
Proteins. 1999; 36:1
Tamoxifen is a famous anticancer drug for treatment of breast cancer.It was approved by FDA in 1998 as the 1st cancer preventive drug. 30 million people are expected to use it.
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INVDOCK Test on Drug Target PredictionINVDOCK Test on Drug Target Prediction
Targets of 4H-tamoxifen (Proteins. 1999; 36:1)
PDB Putative Protein Target Experimental Finding Clinical Implication
1a52 Estrogen Receptor Drug target Confirmed Treatment of breast cancer 36
1akz Uracil-DNA Glycosylase
1ayk Collagenase Inhibited activity ConfirmedTumor cell invasion and cancer metastasis
The complex between the two molecules highly stimulates the response of the T-cells of the immune system. The grp94 protein alone does not have this property. The activity that stimulates the immune response is due to the ability of grp94 to bind different peptides. Characterization of peptide binding site is highly important.
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GRP94 moleculeGRP94 molecule
There was no structure of grp94 protein. Homology modeling was used to predict a structure using another protein with 52% identity.
Recently the structure of grp94 was published. The RMSD between the crystal structure and the model is 1.3A.
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DockingDocking
PatchDock was applied to dock the two molecules, without any binding site constraints. Docking results were clustered in the two cavities:
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GRP94 moleculeGRP94 molecule There is a binding site for inhibitors between the helices. There is another cavity produced by beta sheet on the opposite side.