De novopurification scheme and crystallization conditions yield high-resolution structures of chitinase A and its complex with the inhibitor allosamidin

The purification scheme of chitinase A (ChiA) from S. marcescens has been extensively revised. The pure enzyme crystallizes readily under new crystallization conditions. The ChiA crystal structure has been refined to 1.55 Å resolution and the crystal structure of ChiA co-crystallized with the inhibitor allosamidin has been refined to 1.9 Å resolution. Allosamidin is located in the deep active-site tunnel of ChiA and interacts with three important residues: Glu315, the proton donor of the catalysis, Asp313, which adopts two conformations in the native structure but is oriented towards Glu315 in the inhibitor complex, and Tyr390, which lies opposite Glu315 in the active-site tunnel.