Structural Biology: coenzyme B12 Text Karl-Franzens-Universitaet Homepage of Karl Franzens Universität Graz Homepage of Institut für Chemie, Universität Graz
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Structural formula of B12 - click to view larger image The B12 cofactors constitute a class of fascinating and unusual natural compounds: probaly they are the most complex molecules found in nature, and they are the only known biological molecules with an organometallic bond. They are found as cofactors of enzymes catalyzing unusual and chemically exotic reactions. Our interest in B12 started with structure analyses of isolated B12 compounds, and has been extended to the structure elucidation of proteins with a B12 cofactor.
Our work in the B12 area is pursued in the framework of EU-funded networks, where we cooperate with laboratories in Austria, Germany, Switzerland and the UK. Additional funding is supplied by the Austrian national science foundation FWF.
Link to homepage of the B12 Network



Structure elucidation of B12 proteins

In collaboration with the laboratory of Wolfgang Buckel (Universität Marburg, Germany), we determined the 3D structure of glutamate mutase from Clostrisium cochlearium, and subsequently elucidated the way how the enzyme delivers the highly reactive adenosyl radical (formed by homolysis if the cofactor's organometallic bond) to the substrate. Current studies concern the mechanism of homolysis by determining the structure of enzyme and cofactor mutants (collaboration with Bernhard Kräutler, Innsbruck, and Neil Marsh, Ann Arbor, USA).
A second project concerns the 3D structure elucidation of the related enzyme methyleneglutarate mutase.

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The active site of glutamate mutase - click for a larger picture



Crystallography of isolated B12 cofactors

We investigate the crystal structures of cobalamins as model systems for protein-bound B12 (collaboration with B. Kräutler, Universität Innsbruck and G.Dieckert, Universität Jena, Germany).

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nor-Pseudo-B12 - superposition with



EXAFS spectroscopy of B12

EXAFS spectroscopy of free B12 and of B12 proteins, including glutamate mutase and methyleneglutarate mutase (Collaboration with W. Buckel, Universität Marburg, Germany, W. Meyer-Klaucke, EMBL, Hamburg, Germany and A. Michalowicz, Université de Paris XII, France)

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Superposition of the EXAFS spectra of crystalline and dissolved aquocobalamin
 
 
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