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Structural biology

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Neutron structure and mechanistic investigations of DFPase

In a new article in the Journal Acta Crystallographica D we discuss comprehensively the neutron diffraction structure of DFPase and studies on the reaction mechanism of this enzyme. Three mechanisms proposed for DFPase will be discussed. This includes the original mechanism proposed in 2001 in which histidine residue 287 activates a water molecule for nucleophilic attack on the substrate’s phosphorus atom which itself is activated by coordination to the catalytic calcium ion. The second mechanism proposed in 2006 and currently view as the correct one, includes a covalent phospho-enzyme intermediate. The third mechanism which is discussed and refuted includes water as the nucleophile directly activated by coordination to the calcium.The article point out that besides important structural investigations (the neutron diffraction structure of DFPase yielded important and indispensable information) also mutagenesis and other mechanistic studies are required to derive enzyme reaction mechanisms.

Characterization of the catalytic calcium binding-site in DFPase and comparison with other beta-propeller enzymes

The catalytic calcium binding-site of the enzymes DFPase displays remarkable similarities to metal binding sites in structurally related proteins like Paraoxonase (PON1), Drug Resistance Protein 35 (Drp35) from S. aureus or the Gluconolactonase XC5397 from Xanthomonas campestris. DFPase mutants targeting calcium binding residues and their structural characterization allow new insights with respect to metal binding and catalytic activity. The results are described in a new publication in Chemico-Biological Interactions (CBI). The article is part of a Special Issue of CBI on the occasion of the 10th International Meeting on Cholinesterases, which took place in Croatia in September 2009.