2DW6

Crystal structure of the mutant K184A of D-Tartrate Dehydratase from Bradyrhizobium japonicum complexed with Mg++ and D-tartrate


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.30 Å
  • R-Value Free: 0.232 
  • R-Value Work: 0.209 
  • R-Value Observed: 0.211 

wwPDB Validation   3D Report Full Report


This is version 1.3 of the entry. See complete history


Literature

Evolution of Enzymatic Activities in the Enolase Superfamily: d-Tartrate Dehydratase from Bradyrhizobium japonicum

Yew, W.S.Fedorov, A.A.Fedorov, E.V.Wood, B.M.Almo, S.C.Gerlt, J.A.

(2006) Biochemistry 45: 14598-14608

  • DOI: 10.1021/bi061688g
  • Primary Citation of Related Structures:  
    2DW6, 2DW7

  • PubMed Abstract: 
  • We focus on the assignment of function to and elucidation of structure-function relationships for a member of the mechanistically diverse enolase superfamily encoded by the Bradyrhizobium japonicum genome (bll6730; GI:27381841). As suggested by sequence alignments, the active site contains the same functional groups found in the active site of mandelate racemase (MR) that catalyzes a 1,1-proton transfer reaction: two acid/base catalysts, Lys 184 at the end of the second beta-strand, and a His 322-Asp 292 dyad at the ends of the seventh and sixth beta-strands, respectively, as well as ligands for an essential Mg2+, Asp 213, Glu 239, and Glu 265 at the ends of the third, fourth, and fifth beta-strands, respectively ...

    We focus on the assignment of function to and elucidation of structure-function relationships for a member of the mechanistically diverse enolase superfamily encoded by the Bradyrhizobium japonicum genome (bll6730; GI:27381841). As suggested by sequence alignments, the active site contains the same functional groups found in the active site of mandelate racemase (MR) that catalyzes a 1,1-proton transfer reaction: two acid/base catalysts, Lys 184 at the end of the second beta-strand, and a His 322-Asp 292 dyad at the ends of the seventh and sixth beta-strands, respectively, as well as ligands for an essential Mg2+, Asp 213, Glu 239, and Glu 265 at the ends of the third, fourth, and fifth beta-strands, respectively. We screened a library of 46 acid sugars and discovered that only d-tartrate is dehydrated, yielding oxaloacetate as product. The kinetic constants (kcat = 7.3 s(-1); kcat/KM = 8.5 x 10(4) M(-1) s(-1)) are consistent with assignment of the d-tartrate dehydratase (TarD) function. The kinetic phenotypes of mutants as well as the structures of liganded complexes are consistent with a mechanism in which Lys 184 initiates the reaction by abstraction of the alpha-proton to generate a Mg2+-stabilized enediolate intermediate, and the vinylogous beta-elimination of the 3-OH group is general acid-catalyzed by the His 322, accomplishing the anti-elimination of water. The replacement of the leaving group by solvent-derived hydrogen is stereorandom, suggesting that the enol tautomer of oxaloacetate is the product; this expectation was confirmed by its observation by 1H NMR spectroscopy. Thus, the TarD-catalyzed reaction is a "simple" extension of the two-step reaction catalyzed by MR: base-catalyzed proton abstraction to generate a Mg2+-stabilized enediolate intermediate followed by acid-catalyzed decomposition of that intermediate to yield the product.


    Organizational Affiliation

    Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Bll6730 proteinA, B, C, D389Bradyrhizobium japonicumMutation(s): 1 
EC: 4.2.1.81
UniProt
Find proteins for Q89FH0 (Bradyrhizobium diazoefficiens (strain JCM 10833 / BCRC 13528 / IAM 13628 / NBRC 14792 / USDA 110))
Explore Q89FH0 
Go to UniProtKB:  Q89FH0
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ89FH0
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.30 Å
  • R-Value Free: 0.232 
  • R-Value Work: 0.209 
  • R-Value Observed: 0.211 
  • Space Group: P 61 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 150.997α = 90
b = 150.997β = 90
c = 444.101γ = 120
Software Package:
Software NamePurpose
ADSCdata collection
EPMRphasing
CNSrefinement
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

View Full Validation Report




Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2006-12-19
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2021-11-10
    Changes: Database references, Derived calculations