New Insights into Dihydrofolate Reductase Interactions: Analysis of Pneumocystis carinii and Mouse DHFR Complexes with NADPH and Two Highly Potent Trimethoprim Derivatives

Experimental Data Snapshot

  • Resolution: 2.10 Å
  • R-Value Free: 0.295 
  • R-Value Work: 0.246 
  • R-Value Observed: 0.246 

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Ligand Structure Quality Assessment 

This is version 1.3 of the entry. See complete history


New insights into DHFR interactions: analysis of Pneumocystis carinii and mouse DHFR complexes with NADPH and two highly potent 5-(omega-carboxy(alkyloxy) trimethoprim derivatives reveals conformational correlations with activity and novel parallel ring stacking interactions.

Cody, V.Pace, J.Chisum, K.Rosowsky, A.

(2006) Proteins 65: 959-969

  • DOI: https://doi.org/10.1002/prot.21131
  • Primary Citation of Related Structures:  
    2FZH, 2FZI, 2FZJ

  • PubMed Abstract: 

    Structural data are reported for two highly potent antifolates, 2,4-diamino-5-[3',4'-dimethoxy-5'-(5-carboxy-1-pentynyl)]benzylpyrimidine (PY1011), with 5000-fold selectivity for Pneumocystis carinii dihydrofolate reductase (pcDHFR), relative to rat liver DHFR, and 2,4-diamino-5-[2-methoxy-5-(4-carboxybutyloxy)benzyl]pyrimidine (PY957), that has 80-fold selectivity for pcDHFR. Crystal structures are reported for NADPH ternary complexes with PY957 and pcDHFR, refined to 2.2 A resolution; with PY1011 and pcDHFR, refined to 2.0 A resolution; and with PY1011 and mouse DHFR (mDHFR), refined to 2.2 A resolution. These results reveal that the carboxylate of the omega-carboxyalkyloxy side chain of these inhibitors form ionic interactions with the conserved Arg in the substrate binding pocket of DHFR. These data suggest that the enhanced inhibitory activity of PY1011 compared with PY957 is, in part, due to the favorable contacts with Phe69 of pcDHFR by the methylene carbons of the inhibitor side chain that are oriented by the triple bond of the 1-pentynyl side chain. These contacts are not present in the PY957 pcDHFR complex, or in the PY1011 mDHFR complex. In the structure of mDHFR the site of Phe69 in pcDHFR is occupied by Asn64. These data also revealed a preference for an unusual parallel ring stacking interaction between Tyr35 of the active site helix and Phe199 of the C-terminal beta sheet in pcDHFR and by Tyr33 and Phe179 in mDHFR that is independent of bound ligand. A unique His174-His187 parallel ring stacking interaction was also observed only in the structure of pcDHFR. These ring stacking interactions are rarely found in any other protein families and may serve to enhance protein stability.

  • Organizational Affiliation

    Department of Structural Biology, Hauptman-Woodward Medical Research Institute, Buffalo, New York 14203, USA. cody@hwi.buffalo.edu

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Dihydrofolate reductase206Pneumocystis cariniiMutation(s): 0 
Find proteins for P16184 (Pneumocystis carinii)
Explore P16184 
Go to UniProtKB:  P16184
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP16184
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on NDP

Download Ideal Coordinates CCD File 
C21 H30 N7 O17 P3
Query on DH1

Download Ideal Coordinates CCD File 
C17 H22 N4 O4
Binding Affinity Annotations 
IDSourceBinding Affinity
DH1 BindingDB:  2FZH IC50: 54 (nM) from 1 assay(s)
Binding MOAD:  2FZH IC50: 0.05 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Resolution: 2.10 Å
  • R-Value Free: 0.295 
  • R-Value Work: 0.246 
  • R-Value Observed: 0.246 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 36.871α = 90
b = 42.924β = 95.18
c = 60.925γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

View Full Validation Report

Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2006-12-26
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2023-08-30
    Changes: Data collection, Database references, Derived calculations, Refinement description