Crystal Structure of CobT complexed with 2,5-dimethylaniline and nicotinate mononucleotide

Experimental Data Snapshot

  • Resolution: 2.00 Å
  • R-Value Free: 0.202 
  • R-Value Work: 0.171 

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This is version 1.4 of the entry. See complete history


Capture of a labile substrate by expulsion of water molecules from the active site of nicotinate mononucleotide:5,6-dimethylbenzimidazole phosphoribosyltransferase (CobT) from Salmonella enterica.

Cheong, C.G.Escalante-Semerena, J.C.Rayment, I.

(2002) J Biol Chem 277: 41120-41127

  • DOI: https://doi.org/10.1074/jbc.M203535200
  • Primary Citation of Related Structures:  
    1L4B, 1L4E, 1L4F, 1L4G, 1L4H, 1L4K, 1L4L, 1L4M, 1L5O

  • PubMed Abstract: 

    Nicotinate mononucleotide (NaMN):5,6-dimethylbenzimidazole (DMB) phosphoribosyltransferase (CobT) from Salmonella enterica plays a central role in the synthesis of alpha-ribazole-5'-phosphate, an intermediate for the lower ligand of cobalamin. In earlier studies it proved difficult to obtain the structure of CobT bound to NaMN because it is hydrolyzed in the crystal lattice in the absence of the second substrate DMB. In an effort to map the reaction pathway of this enzyme, NaMN was captured in the active site with the substrate analogs 4,5-dimethyl-1,2-phenylenediamine, 4-methylcatechol, indole, 3,4-dimethylaniline, 2,5-dimethylaniline, 3,4-dimethylphenol, and 2-amino-p-cresol. Structures of these complexes reveal that they exclude water molecules responsible for the hydrolysis from the active site. These structures, together with the early complexes with alpha-ribazole-5'-phosphate and DMB, provide a complete description of the reaction pathway. They demonstrate that the nicotinate moiety and phosphate do not appear to move significantly between reactants and products but that the aromatic base and ribose moiety each move approximately 1.2 A toward each other in the transformation. This study also reveals that, like many other nucleotide binding proteins, coordination of DMB is accompanied by a disorder-order transition in a surface loop. The structure of apo-CobT is also reported.

  • Organizational Affiliation

    Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706, USA.

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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Nicotinate-nucleotide--dimethylbenzimidazole phosphoribosyltransferase356Salmonella entericaMutation(s): 0 
Gene Names: cobt
Find proteins for Q05603 (Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720))
Explore Q05603 
Go to UniProtKB:  Q05603
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ05603
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on NCN

Download Ideal Coordinates CCD File 
C11 H14 N O9 P
Query on XYD

Download Ideal Coordinates CCD File 
C8 H11 N
Experimental Data & Validation

Experimental Data

  • Resolution: 2.00 Å
  • R-Value Free: 0.202 
  • R-Value Work: 0.171 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 71.77α = 90
b = 90β = 90
c = 47.58γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XDSdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2002-09-07
    Type: Initial release
  • Version 1.1: 2008-04-28
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Derived calculations, Version format compliance
  • Version 1.3: 2016-06-15
    Changes: Database references
  • Version 1.4: 2023-08-16
    Changes: Data collection, Database references, Derived calculations, Refinement description