1MAE: The Active Site Structure Of Methylamine Dehydrogenase: Hydrazines Identify C6 As The Reactive Site Of The Tryptophan Derived Quinone Cofactor

To identify the reactive part of the orthoquinone function of the tryptophan-derived cofactor found in methylamine dehydrogenase (MADH), we have determined the crystal structures of MADH from Thiobacillus versutus inhibited by methylhydrazine and (2,2,2-trifluoroethyl)hydrazine. Extra electron density attached to C6 of the tryptophyl tryptophanquinone cofactor shows that this atom and not C7 is the reactive part of the ortho-quinone moiety. The density retained after hydrazine inhibition is much less extensive than expected, however, suggesting that partial breakdown of the inhibitors after reaction with the cofactor may take place. A detailed description is presented of the cofactor environment in an improved model of MADH which now includes information from the recently determined gene sequence of the cofactor-containing subunit [Ubbink, M., van Kleef, M.A.G., Kleinjan, D., Hoitink, C.W.G., Huitema, F., Beintema, J.J., Duine, J.A., & Canters, G.W. (1991) Eur. J. Biochem. 202, 1003-1012]. We hypothesize that Asp76 is responsible for proton abstraction from the alpha-carbon of the substrate during catalysis.
PDB ID: 1MAEDownload
MMDB ID: 50234
PDB Deposition Date: 1992/5/20
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 2.8  Å
Source Organism:
Similar Structures:
Biological Unit for 1MAE: tetrameric; determined by author
Molecular Components in 1MAE
Label Count Molecule
Proteins (4 molecules)
Methylamine Dehydrogenase (Light Subunit)
Molecule annotation
Methylamine Dehydrogenase (Heavy Subunit)
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB