P. putida mandelate racemase co-crystallized with 3,3,3-trifluoro-2-hydroxy-2-(trifluoromethyl) propionic acid

Experimental Data Snapshot

  • Resolution: 1.68 Å
  • R-Value Free: 0.193 
  • R-Value Work: 0.169 
  • R-Value Observed: 0.171 

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This is version 1.5 of the entry. See complete history


Potent inhibition of mandelate racemase by a fluorinated substrate-product analogue with a novel binding mode.

Nagar, M.Lietzan, A.D.St Maurice, M.Bearne, S.L.

(2014) Biochemistry 53: 1169-1178

  • DOI: https://doi.org/10.1021/bi401703h
  • Primary Citation of Related Structures:  
    4FP1, 4HNC, 4M6U

  • PubMed Abstract: 

    Mandelate racemase (MR) from Pseudomonas putida catalyzes the Mg(2+)-dependent 1,1-proton transfer that interconverts the enantiomers of mandelate. Because trifluorolactate is also a substrate of MR, we anticipated that replacing the phenyl rings of the competitive, substrate-product analogue inhibitor benzilate (Ki = 0.7 mM) with trifluoromethyl groups might furnish an inhibitor. Surprisingly, the substrate-product analogue 3,3,3-trifluoro-2-hydroxy-2-(trifluoromethyl)propanoate (TFHTP) was a potent competitive inhibitor [Ki = 27 ± 4 μM; cf. Km = 1.2 mM for both (R)-mandelate and (R)-trifluorolactate]. To understand the origins of this high binding affinity, we determined the X-ray crystal structure of the MR-TFHTP complex to 1.68 Å resolution. Rather than chelating the active site Mg(2+) with its glycolate moiety, like other ground state analogues, TFHTP exhibited a novel binding mode with the two trifluoromethyl groups closely packed against the 20s loop and the carboxylate bridging the two active site Brønsted acid-base catalysts Lys 166 and His 297. Recognizing that positioning a carboxylate between the Brønsted acid-base catalysts could yield an inhibitor, we showed that tartronate was a competitive inhibitor of MR (Ki = 1.8 ± 0.1 mM). The X-ray crystal structure of the MR-tartronate complex (1.80 Å resolution) revealed that the glycolate moiety of tartronate chelated the Mg(2+) and that the carboxylate bridged Lys 166 and His 297. Models of tartronate in monomers A and B of the crystal structure mimicked the binding orientations of (S)-mandelate and that anticipated for (R)-mandelate, respectively. For the latter monomer, the 20s loop appeared to be disordered, as it also did in the X-ray structure of the MR triple mutant (C92S/C264S/K166C) complexed with benzilate, which was determined to 1.89 Å resolution. These observations indicate that the 20s loop likely undergoes a significant conformational change upon binding (R)-mandelate. In general, our observations suggest that inhibitors of other enolase superfamily enzymes may be designed to capitalize on the recognition of the active site Brønsted acid-base catalysts as binding determinants.

  • Organizational Affiliation

    Department of Biochemistry and Molecular Biology, Dalhousie University , Halifax, Nova Scotia B3H 4R2, Canada.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Mandelate racemase
A, B
383Pseudomonas putidaMutation(s): 0 
Gene Names: mdlA
Find proteins for P11444 (Pseudomonas putida)
Explore P11444 
Go to UniProtKB:  P11444
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP11444
Sequence Annotations
  • Reference Sequence
Small Molecules
Binding Affinity Annotations 
IDSourceBinding Affinity
BFM PDBBind:  4FP1 Ki: 2.70e+4 (nM) from 1 assay(s)
Binding MOAD:  4FP1 Ki: 2.70e+4 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Resolution: 1.68 Å
  • R-Value Free: 0.193 
  • R-Value Work: 0.169 
  • R-Value Observed: 0.171 
  • Space Group: I 4 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 148.87α = 90
b = 148.87β = 90
c = 169.64γ = 90
Software Package:
Software NamePurpose
MD2data collection
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2013-06-26
    Type: Initial release
  • Version 1.1: 2014-03-05
    Changes: Database references
  • Version 1.2: 2014-03-12
    Changes: Database references
  • Version 1.3: 2018-01-24
    Changes: Structure summary
  • Version 1.4: 2018-01-31
    Changes: Structure summary
  • Version 1.5: 2023-09-13
    Changes: Data collection, Database references, Derived calculations, Refinement description