2A7K

carboxymethylproline synthase (CarB) from pectobacterium carotovora, apo enzyme


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.24 Å
  • R-Value Free: 0.238 
  • R-Value Work: 0.185 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Structural and Mechanistic Studies on Carboxymethylproline Synthase (CarB), a Unique Member of the Crotonase Superfamily Catalyzing the First Step in Carbapenem Biosynthesis.

Sleeman, M.C.Sorensen, J.L.Batchelar, E.T.McDonough, M.A.Schofield, C.J.

(2005) J.Biol.Chem. 280: 34956-34965

  • DOI: 10.1074/jbc.M507196200
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • The first step in the biosynthesis of the medicinally important carbapenem family of beta-lactam antibiotics is catalyzed by carboxymethylproline synthase (CarB), a unique member of the crotonase superfamily. CarB catalyzes formation of (2S,5S)-carbo ...

    The first step in the biosynthesis of the medicinally important carbapenem family of beta-lactam antibiotics is catalyzed by carboxymethylproline synthase (CarB), a unique member of the crotonase superfamily. CarB catalyzes formation of (2S,5S)-carboxymethylproline [(2S,5S)-t-CMP] from malonyl-CoA and l-glutamate semialdehyde. In addition to using a cosubstrate, CarB catalyzes C-C and C-N bond formation processes as well as an acyl-coenzyme A hydrolysis reaction. We describe the crystal structure of CarB in the presence and absence of acetyl-CoA at 2.24 A and 3.15 A resolution, respectively. The structures reveal that CarB contains a conserved oxy-anion hole probably required for decarboxylation of malonyl-CoA and stabilization of the resultant enolate. Comparison of the structures reveals that conformational changes (involving His(229)) in the cavity predicted to bind l-glutamate semialdehyde occur on (co)substrate binding. Mechanisms for the formation of the carboxymethylproline ring are discussed in the light of the structures and the accompanying studies using isotopically labeled substrates; cyclization via 1,4-addition is consistent with the observed labeling results (providing that hydrogen exchange at the C-6 position of carboxymethylproline does not occur). The side chain of Glu(131) appears to be positioned to be involved in hydrolysis of the carboxymethylproline-CoA ester intermediate. Labeling experiments ruled out the possibility that hydrolysis proceeds via an anhydride in which water attacks a carbonyl derived from Glu(131), as proposed for 3-hydroxyisobutyryl-CoA hydrolase. The structural work will aid in mutagenesis studies directed at altering the selectivity of CarB to provide intermediates for the production of clinically useful carbapenems.


    Organizational Affiliation

    Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
CarB
A, B, C, D, E, F, G, H, I
250Pectobacterium carotovorum subsp. carotovorumMutation(s): 0 
Gene Names: carB
EC: 2.3.1.226
Find proteins for Q9XB60 (Pectobacterium carotovorum subsp. carotovorum)
Go to UniProtKB:  Q9XB60
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.24 Å
  • R-Value Free: 0.238 
  • R-Value Work: 0.185 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 87.207α = 90.00
b = 89.860β = 90.00
c = 264.582γ = 90.00
Software Package:
Software NamePurpose
HKL-2000data reduction
SCALEPACKdata scaling
CCP4data scaling
RESOLVEphasing
REFMACrefinement
SCALAdata scaling
SHELXphasing
PDB_EXTRACTdata extraction
SHELXDphasing
MOSFLMdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2005-08-23
    Type: Initial release
  • Version 1.1: 2008-04-01
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Derived calculations, Version format compliance