The refined structure of the quinoprotein methanol dehydrogenase from Methylobacterium extorquens at 1.94 A

Structure. 1995 Feb 15;3(2):177-87. doi: 10.1016/s0969-2126(01)00148-4.


Background: Methanol dehydrogenase (MDH) is a bacterial periplasmic quinoprotein; it has pyrrolo-quinoline quinone (PQQ) as its prosthetic group, requires Ca2+ for activity and uses cytochrome cL as its electron acceptor. Low-resolution structures of MDH have already been determined.

Results: The structure of the alpha 2 beta 2 tetramer of MDH from Methylobacterium extorquens has now been determined at 1.94 A with an R-factor of 19.85%.

Conclusions: The alpha-subunit of MDH has an eight-fold radial symmetry, with its eight beta-sheets stabilized by a novel tryptophan docking motif. The PQQ in the active site is held in place by a coplanar tryptophan and by a novel disulphide ring formed between adjacent cysteines which are bonded by an unusual non-planar trans peptide bond. One of the carbonyl oxygens of PQQ is bonded to the Ca2+, probably facilitating attack on the substrate, and the other carbonyl oxygen is out of the plane of the ring, confirming the presence of the predicted free-radical semiquinone form of the prosthetic group.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alcohol Oxidoreductases / chemistry*
  • Amino Acid Sequence
  • Binding Sites
  • Calcium / chemistry
  • Coenzymes / chemistry
  • Computer Graphics
  • Crystallography, X-Ray
  • Gram-Negative Aerobic Bacteria / enzymology*
  • Models, Molecular
  • Molecular Sequence Data
  • Molecular Structure
  • PQQ Cofactor
  • Protein Conformation*
  • Quinolones / chemistry


  • Coenzymes
  • Quinolones
  • PQQ Cofactor
  • Alcohol Oxidoreductases
  • alcohol dehydrogenase (acceptor)
  • Calcium