2ISK

BluB bound to flavin anion (charge transfer complex)

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.10 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.203 
  • R-Value Observed: 0.206 

wwPDB Validation   3D Report Full Report


This is version 1.2 of the entry. See complete history. 


Literature

BluB cannibalizes flavin to form the lower ligand of vitamin B12.

Taga, M.E., Larsen, N.A., Howard-Jones, A.R., Walsh, C.T., Walker, G.C.

(2007) Nature 446: 449-453

  • DOI: 10.1038/nature05611
  • Primary Citation of Related Structures:  
    2ISL, 2ISK, 2ISJ

  • PubMed Abstract: 

    • Vitamin B12 (cobalamin) is among the largest known non-polymeric natural products, and the only vitamin synthesized exclusively by microorganisms. The biosynthesis of the lower ligand of vitamin B(12), 5,6-dimethylbenzimidazole (DMB), is poorly understood ...

    Vitamin B12 (cobalamin) is among the largest known non-polymeric natural products, and the only vitamin synthesized exclusively by microorganisms. The biosynthesis of the lower ligand of vitamin B(12), 5,6-dimethylbenzimidazole (DMB), is poorly understood. Recently, we discovered that a Sinorhizobium meliloti gene, bluB, is necessary for DMB biosynthesis. Here we show that BluB triggers the unprecedented fragmentation and contraction of the bound flavin mononucleotide cofactor and cleavage of the ribityl tail to form DMB and D-erythrose 4-phosphate. Our structural analysis shows that BluB resembles an NAD(P)H-flavin oxidoreductase, except that its unusually tight binding pocket accommodates flavin mononucleotide but not NAD(P)H. We characterize crystallographically an early intermediate along the reaction coordinate, revealing molecular oxygen poised over reduced flavin. Thus, BluB isolates and directs reduced flavin to activate molecular oxygen for its own cannibalization. This investigation of the biosynthesis of DMB provides clarification of an aspect of vitamin B12 that was otherwise incomplete, and may contribute to a better understanding of vitamin B12-related disease.

    Related Citations: 
    • Sinorhizobium meliloti bluB is necessary for production of 5,6-dimethylbenzimidazole, the lower ligand of B12.
      (2006) Proc Natl Acad Sci U S A 103: 4634
    Organizational Affiliation: 

    Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.



Macromolecules
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(by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
BluBA, B, C, D, E, F, G, H230Sinorhizobium melilotiMutation(s): 0 
Gene Names: bluB
EC: 1.13.11.79
Find proteins for Q92PC8 (Rhizobium meliloti (strain 1021))
Explore Q92PC8 
Go to UniProtKB:  Q92PC8
Protein Feature View
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  • Reference Sequence
Small Molecules
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.10 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.203 
  • R-Value Observed: 0.206 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 63.449α = 90
b = 169.872β = 89.99
c = 90.954γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
MOLREPphasing
CNSrefinement
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2007-03-27
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance