Serendipitous crystallization and structure determination of cyanase (CynS) fromSerratia proteamaculans

Abstract

Cyanate hydratase (CynS) catalyzes the decomposition of cyanate and bicarbonate into ammonia and carbon dioxide. Here, the serendipitous crystallization of CynS fromSerratia proteamaculans(SpCynS) is reported. SpCynS was crystallized as an impurity and its identity was determined using mass-spectrometric analysis. The crystals belonged to space groupP1 and diffracted to 2.1 Å resolution. The overall structure of SpCynS is very similar to a previously determined structure of CynS fromEscherichia coli. Density for a ligand bound to the SpCynS active site was observed, but could not be unambiguously identified. Additionally, glycerol molecules bound at the entry to the active site of the enzyme indicate conserved residues that might be important for the trafficking of substrates and products.