Crystallization of dienelactone hydrolase in two space groups: structural changes caused by crystal packing

Abstract

Dienelactone hydrolase (DLH) is a monomeric protein with a simple α/β-hydrolase fold structure. It readily crystallizes in space groupP212121from either a phosphate or ammonium sulfate precipitation buffer. Here, the structure of DLH at 1.85 Å resolution crystallized in space groupC2 with two molecules in the asymmetric unit is reported. When crystallized in space groupP212121DLH has either phosphates or sulfates bound to the protein in crucial locations, one of which is located in the active site, preventing substrate/inhibitor binding. Another is located on the surface of the enzyme coordinated by side chains from two different molecules. Crystallization in space groupC2 from a sodium citrate buffer results in new crystallographic protein–protein interfaces. The protein backbone is highly similar, but new crystal contacts cause changes in side-chain orientations and in loop positioning. In regions not involved in crystal contacts, there is little change in backbone or side-chain configuration. The flexibility of surface loops and the adaptability of side chains are important factors enabling DLH to adapt and form different crystal lattices.