Structural Proteomics for Drug Target Validation
Comprehensive structural data integration using ToolUniverse tools across PDB, AlphaFold, GPCRdb, SAbDab, and proteomics databases for drug target validation.
LOOK UP DON'T GUESS
- PDB structures/resolutions:
PDBeSIFTSgetbeststructures and RCSBGraphQLgetstructuresummary
- AlphaFold confidence:
alphafoldgetsummary
- Ligands/affinities:
PDBegetstructureligands and BindingDBgetligandsby_uniprot
- Druggability:
ProteinsPluspredictbinding_sites
COMPUTE, DON'T DESCRIBE
When analysis requires computation (statistics, data processing, scoring, enrichment), write and run Python code via Bash. Don't describe what you would do — execute it and report actual results. Use ToolUniverse tools to retrieve data, then Python (pandas, scipy, statsmodels, matplotlib) to analyze it.
Domain Reasoning
Resolution determines valid conclusions: <2A = atom positions visible; 2-3A = side chains reliable, drug design supported; >3A = backbone only, binding site unreliable. Do not over-interpret low-resolution structures.
Tool Inventory
PDB (RCSB)
RCSBAdvSearchsearchstructures (querytype, queryvalue, rows), RCSBDatagetentry (entryid), RCSBGraphQLgetstructuresummary (pdbid), RCSBGraphQLgetligandinfo (pdbid), RCSBgetchemicalcomponent (comp_id)
PDB (PDBe)
pdbegetentrysummary (pdbid), PDBegetstructureligands (pdbid), PDBegetboundmolecules (pdbid), PDBeSearchsearchstructures (query, rows), PDBeSIFTSgetbeststructures (uniprotid), PDBeSIFTSgetallstructures (uniprotid), PDBeKBgetligandsites (pdbid), PDBeKBgetinterfaceresidues (pdbid), PDBeValidationgetqualityscores (pdbid)
PDBe PISA
PDBePISAgetinterfaces (pdbid), PDBePISAgetassemblies (pdbid)
AlphaFold
alphafoldgetprediction (qualifier=UniProt), alphafoldgetsummary (qualifier), alphafoldgetannotations (qualifier)
Binding Sites
ProteinsPluspredictbindingsites (pdbid, chain), BindingDBgetligandsbyuniprot (uniprotid), BindingDBgetligandsbypdb (pdbid), BindingDBgettargetsbycompound (smiles)
Foldseek
Foldseeksearchstructure (sequence, mode="tmalign"), Foldseekgetresult (ticket)
GPCRdb
GPCRdbgetprotein (protein), GPCRdbgetstructures (protein), GPCRdbgetligands (protein), GPCRdbgetmutations (protein). Accepts entry names, gene symbols (auto-converted to {symbol.lower()}_human), or UniProt accessions.
SAbDab
SAbDabsearchstructures (query/antigen), SAbDabgetstructure (pdbid), TheraSAbDabsearchtherapeutics (query), TheraSAbDabsearchbytarget (target)
Domains
InterProgetproteindomains (uniprotid), Pfamgetproteinannotations (uniprotid), UniProtgetentrybyaccession (accession)
Proteomics
ProteomeXchangesearchdatasets (query), ProteomeXchangegetdataset (dataset_id)
Workflow 1: Find All Structures for a Drug Target
Phase 0: Resolve protein → UniProt ID, gene symbol, organism
Phase 1: PDBeSIFTS_get_best_structures → RCSBGraphQL_get_structure_summary → PDBeValidation
Phase 2: alphafold_get_prediction/summary → compare pLDDT with experimental coverage
Phase 3: IF GPCR → GPCRdb; IF antibody target → SAbDab/TheraSAbDab
Phase 4: InterPro/Pfam domain mapping → identify unresolved regions
Phase 5: Summary table (PDB ID, method, resolution, ligands, coverage, quality)
Decisions: Resolution <2.5A for drug design. X-ray > Cryo-EM > NMR > AlphaFold for binding sites. Holo > apo structures.
Workflow 2: Identify Binding Pocket Ligands
Phase 1: PDBe_get_structure_ligands + RCSBGraphQL_get_ligand_info + PDBe_KB_get_ligand_sites
Phase 2: ProteinsPlus_predict_binding_sites → druggability score, pocket residues
Phase 3: BindingDB_get_ligands_by_pdb/uniprot → Ki, Kd, IC50
Phase 4: RCSB_get_chemical_component for key ligands
Filter artifacts: GOL, EDO, SO4, PEG, ACT, CL, NA. Keep cofactors (ATP, NAD, HEM) and catalytic metals (ZN, MG) if relevant.
Workflow 3: Cross-Validate Drug Binding
Phase 1: Find co-crystal structures → filter for drug/analogs
Phase 2: BindingDB affinity data (Ki, Kd, IC50)
Phase 3: ProteinsPlus + PDBe-KB binding site characterization
Phase 4: PDBeValidation quality → binding site well-resolved?
Phase 5: AlphaFold + Foldseek structural comparison
Phase 6: GPCR-specific (if applicable) → active/inactive states, pharmacology, resistance mutations
Phase 7: Antibody-specific (if applicable) → epitope mapping
Phase 8: Evidence integration
Tool Parameter Gotchas
| Tool |
Mistake |
Correct |
alphafoldgetprediction/summary |
uniprot_id |
qualifier |
GPCRdbgetprotein |
gene_name |
protein |
PDBeSIFTSgetbest_structures |
gene symbol |
uniprot_id (e.g., "P04637") |
Foldseeksearchstructure |
mode="3diaa" |
mode="tmalign" |
SAbDabsearchstructures |
name |
query or antigen |
RCSBgetchemical_component |
ligand_id |
comp_id |
Evidence Grading
| Tier |
Confidence |
| T1 |
Co-crystal (<2.5A) + binding affinity data |
| T2 |
Experimental structure + computational prediction |
| T3 |
AlphaFold + pocket analysis + known ligand analogs |
| T4 |
Homology model or low-resolution only |
Interpretation
| Metric |
High |
Acceptable |
Caution |
| Resolution |
<2.0A (X-ray) / <3.0A (cryo-EM) |
2.0-2.5A / 3.0-4.0A |
>3.0A / >4.5A |
| R-free |
<0.25 |
0.25-0.30 |
>0.30 |
| AlphaFold pLDDT |
>90 |
70-90 |
<70 (disordered) |
DoGSiteScorer >0.6 = druggable; <0.4 = unlikely druggable. PISA assemblies should be cross-validated with SEC-MALS/native MS.
Limitations
- BindingDB: 60s+ for popular targets
- AlphaFold: lacks ligand context
- GPCRdb: Class A-F GPCRs only
- PDBePISA:
operation is internal, not a public parameter