3G7K

Crystal Structure of Methylitaconate-delta-isomerase


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.7 Å
  • R-Value Free: 0.256 
  • R-Value Work: 0.200 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

Crystal structure and putative mechanism of 3-methylitaconate-delta-isomerase from Eubacterium barkeri

Velarde, M.Macieira, S.Hilberg, M.Broker, G.Tu, S.-M.Golding, B.T.Pierik, A.J.Buckel, W.Messerschmidt, A.

(2009) J.Mol.Biol. 391: 609-620

  • DOI: 10.1016/j.jmb.2009.06.052

  • PubMed Abstract: 
  • 3-Methylitaconate-Delta-isomerase (Mii) participates in the nicotinate fermentation pathway of the anaerobic soil bacterium Eubacterium barkeri (order Clostridiales) by catalyzing the reversible conversion of (R)-3-methylitaconate (2-methylene-3-meth ...

    3-Methylitaconate-Delta-isomerase (Mii) participates in the nicotinate fermentation pathway of the anaerobic soil bacterium Eubacterium barkeri (order Clostridiales) by catalyzing the reversible conversion of (R)-3-methylitaconate (2-methylene-3-methylsuccinate) to 2,3-dimethylmaleate. The enzyme is also able to catalyze the isomerization of itaconate (methylenesuccinate) to citraconate (methylmaleate) with ca 10-fold higher K(m) but > 1000-fold lower k(cat). The gene mii from E. barkeri was cloned and expressed in Escherichia coli. The protein produced with a C-terminal Strep-tag exhibited the same specific activity as the wild-type enzyme. The crystal structure of Mii from E. barkeri has been solved at a resolution of 2.70 A. The asymmetric unit of the P2(1)2(1)2(1) unit cell with parameters a = 53.1 A, b = 142.3 A, and c = 228.4 A contains four molecules of Mii. The enzyme belongs to a group of isomerases with a common structural feature, the so-called diaminopimelate epimerase fold. The monomer of 380 amino acid residues has two topologically similar domains exhibiting an alpha/beta-fold. The active site is situated in a cleft between these domains. The four Mii molecules are arranged as a tetramer with 222 symmetry for the N-terminal domains. The C-terminal domains have different relative positions with respect to the N-terminal domains resulting in a closed conformation for molecule A and two distinct open conformations for molecules B and D. The C-terminal domain of molecule C is disordered. The Mii active site contains the putative catalytic residues Lys62 and Cys96, for which mechanistic roles are proposed based on a docking experiment of the Mii substrate complex. The active sites of Mii and the closely related PrpF, most likely a methylaconitate Delta-isomerase, have been compared. The overall architecture including the active-site Lys62, Cys96, His300, and Ser17 (Mii numbering) is similar. This positioning of (R)-3-methylitaconate allows Cys96 (as thiolate) to deprotonate C-3 and (as thiol) to donate a proton to the methylene carbon atom of the resulting allylic carbanion. Interestingly, the active site of isopentenyl diphosphate isomerase type I also contains a cysteine that cooperates with glutamate rather than lysine. It has been proposed that the initial step in this enzyme is a protonation generating a tertiary carbocation intermediate.


    Organizational Affiliation

    Department of Proteomics and Signal Transduction, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
3-methylitaconate isomerase
A, B, C, D
391Eubacterium barkeriMutation(s): 0 
Gene Names: mii
EC: 5.3.3.6
Find proteins for Q0QLE6 (Eubacterium barkeri)
Go to UniProtKB:  Q0QLE6
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.7 Å
  • R-Value Free: 0.256 
  • R-Value Work: 0.200 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 53.078α = 90.00
b = 142.077β = 90.00
c = 228.452γ = 90.00
Software Package:
Software NamePurpose
SCALEPACKdata scaling
REFMACrefinement
HKL-2000data reduction
MAR345dtbdata collection
MOLREPphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2009-07-21
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance