2012 DOCK tutorial with Streptavidin
For additional Rizzo Lab tutorials see DOCK Tutorials.
Contents
I. Introduction
DOCK
DOCK was developed by Irwin D. "Tack" Kuntz, Jr., PhD and colleagues at UCSF. Please see the webpage at UCSF DOCK.
DOCK is a molecular docking program used in drug discovery. This program, given a protein active site and a small molecule, tries to predict the correct binding mode of the small molecule in the active site, and the associated binding energy. Small molecules with highly favorable binding energies could be new drug leads. This makes DOCK a valuable drug discovery tool. DOCK is typically used to screen massive libraries of millions of compounds against a protein to isolate potential drug leads. These leads are then further studied, and could eventually result in a new, marketable drug. DOCK is works well as a screening procedure for generating leads, but not nearly as well for optimization of those leads. Original DOCK used only rigid body docking, DOCK 4.0, however, introduced flexible ligand docking by either a)incremental construction or b)random search.
Incremental construction (aka anchor and grow) could be roughly described by a three step process: 1) rigid portion of ligand (anchor) is docked by geometrical methods 2) non-rigid segments added; energy minimized 3) the resulting configurations are 'pruned' and energy re-minimized, yielding the docked configurations
Random search method involves docking random conformations of ligand as independent rigid objects. The number of conformations allowed per rotatable bond is arbitrary and user controlled. The receptor is always held rigid in DOCK 4.0.
Streptavidin & Biotin
Streptavidin is a tetrameric prokaryoke protein that binds the co-enzyme biotin with an extremely high affinity. The streptavidin monomer is composed of eight antiparallel beta-strands which folds to give a beta barrel tertiary structure. A biotin binding-site is located at one end of each β-barrel, which has a high affinity as well as a high avidity for biotin. Four identical streptavidin monomers associate to give streptavidin’s tetrameric quaternary structure. The biotin binding-site in each barrel consists of residues from the interior of the barrel, together with a conserved Trp120 from neighbouring subunit. In this way, each subunit contributes to the binding site on the neighboring subunit, and so the tetramer can also be considered a dimer of functional dimers.
Biotin is a water soluble B-vitamin complex which is composed of an ureido (tetrahydroimidizalone) ring fused with a tetrahydrothiophene ring. It is a co-enzyme that is required in the metabolism of fatty acids and leucine. It is also involved in gluconeogenisis.
II. Preparing the Enzyme and Ligand in Chimera
Downloading the PDB complex
DOCKprep in Chimera
III. Generation of Enzyme Surface and Spheres
Enzyme Surface
Spheres
IV. Generation of Box and Grid
Box
Grid
V. Docking a Single Molecule
Rigid Docking Protocol
The rigid.in file is:
ligand_atom_file 1DF8.ligand.mol2 limit_max_ligands no skip_molecule no read_mol_solvation no calculate_rmsd yes use_rmsd_reference_mol no use_database_filter no orient_ligand yes automated_matching yes receptor_site_file selected_spheres.sph max_orientations 1000 critical_points no chemical_matching no use_ligand_spheres no use_internal_energy yes internal_energy_rep_exp 12 flexible_ligand no bump_filter no score_molecules yes contact_score_primary no contact_score_secondary no grid_score_primary yes grid_score_secondary no grid_score_rep_rad_scale 1 grid_score_vdw_scale 1 grid_score_es_scale 1 grid_score_grid_prefix grid dock3.5_score_secondary no continuous_score_secondary no gbsa_zou_score_secondary no gbsa_hawkins_score_secondary no amber_score_secondary no minimize_ligand yes simplex_max_iterations 1000 simplex_tors_premin_iterations 0 simplex_max_cycles 1 simplex_score_converge 0.1 simplex_cycle_converge 1.0 simplex_trans_step 1.0 simplex_rot_step 0.1 simplex_tors_step 10.0 simplex_random_seed 0 simplex_restraint_min no atom_model all vdw_defn_file vdw_AMBER_parm99.defn flex_defn_file flex.defn flex_drive_file flex_drive.tbl ligand_outfile_prefix rigid write_orientations no num_scored_conformers 5000 write_conformations no cluster_conformations yes cluster_rmsd_threshold 2.0 rank_ligands no
Flexible Docking Protocol
The flex.in file is:
ligand_atom_file 1DF8.ligand.mol2 limit_max_ligands no skip_molecule no read_mol_solvation no calculate_rmsd yes use_rmsd_reference_mol no use_database_filter no orient_ligand yes automated_matching yes receptor_site_file selected_spheres.sph max_orientations 1000 critical_points no chemical_matching no use_ligand_spheres no use_internal_energy yes internal_energy_rep_exp 12 flexible_ligand yes min_anchor_size 40 pruning_use_clustering yes pruning_max_orients 100 pruning_clustering_cutoff 100 pruning_conformer_score_cutoff 25.0 use_clash_overlap no write_growth_tree no bump_filter no score_molecules yes contact_score_primary no contact_score_secondary no grid_score_primary yes grid_score_secondary no grid_score_rep_rad_scale 1 grid_score_vdw_scale 1 grid_score_es_scale 1 grid_score_grid_prefix grid dock3.5_score_secondary no continuous_score_secondary no gbsa_zou_score_secondary no gbsa_hawkins_score_secondary no amber_score_secondary no minimize_ligand yes minimize_anchor yes minimize_flexible_growth yes use_advanced_simplex_parameters no simplex_max_cycles 1 simplex_score_converge 0.1 simplex_cycle_converge 1.0 simplex_trans_step 1.0 simplex_rot_step 0.1 simplex_tors_step 10.0 simplex_anchor_max_iterations 500 simplex_grow_max_iterations 20 simplex_grow_tors_premin_iterations 20 simplex_random_seed 0 simplex_restraint_min no atom_model all vdw_defn_file vdw_AMBER_parm99.defn flex_defn_file flex.defn flex_drive_file flex_drive.tbl ligand_outfile_prefix flex write_orientations no num_scored_conformers 5000 write_conformations no cluster_conformations yes cluster_rmsd_threshold 2.0 rank_ligands no
Docking Results
VI. Virtual Screening
Sample flex docking input file
ligand_atom_file 3_t60.mol2 limit_max_ligands no skip_molecule no read_mol_solvation no calculate_rmsd no use_database_filter yes dbfilter_max_heavy_atoms 999 dbfilter_min_heavy_atoms 0 dbfilter_max_rot_bonds 999 dbfilter_min_rot_bonds 0 dbfilter_max_molwt 9999.0 dbfilter_min_molwt 0.0 dbfilter_max_formal_charge 10.0 dbfilter_min_formal_charge -10.0 orient_ligand yes automated_matching yes receptor_site_file selected_spheres.sph max_orientations 1000 critical_points no chemical_matching no use_ligand_spheres no use_internal_energy yes internal_energy_rep_exp 12 flexible_ligand yes min_anchor_size 5 pruning_use_clustering yes pruning_max_orients 100 pruning_clustering_cutoff 100 pruning_conformer_score_cutoff 25.0 use_clash_overlap no write_growth_tree no bump_filter no score_molecules yes contact_score_primary no contact_score_secondary no grid_score_primary yes grid_score_secondary no grid_score_rep_rad_scale 1 grid_score_vdw_scale 1 grid_score_es_scale 1 grid_score_grid_prefix grid dock3.5_score_secondary no continuous_score_secondary no gbsa_zou_score_secondary no gbsa_hawkins_score_secondary no amber_score_secondary no minimize_ligand yes minimize_anchor yes minimize_flexible_growth yes use_advanced_simplex_parameters no simplex_max_cycles 1 simplex_score_converge 0.1 simplex_cycle_converge 1.0 simplex_trans_step 1.0 simplex_rot_step 0.1 simplex_tors_step 10.0 simplex_anchor_max_iterations 1000 simplex_grow_max_iterations 20 simplex_grow_tors_premin_iterations 0 simplex_random_seed 0 simplex_restraint_min no atom_model all vdw_defn_file vdw.defn flex_defn_file flex.defn flex_drive_file flex_drive.tbl ligand_outfile_prefix vs write_orientations no num_scored_conformers 1 rank_ligands yes max_ranked_ligands 20000
Sample script with openmpi using 8 processors on seawulf
#! /bin/tcsh
#PBS -l nodes=4:ppn=2
#PBS -l walltime=200:00:00
#PBS -o zzz.qsub.out
#PBS -j oe
#PBS -V
set nprocs = `wc -l $PBS_NODEFILE | awk '{print $1}'`
echo "Running on ${nprocs} processors"
cd /nfs/user03/sudipto/1DF8_vs
mpirun -np $nprocs dock6.mpi -i vs.in -o vs.out
