Production of crystallizable human chymase from a Bacillus subtilis system

A Bacillus subtilis strain deficient in seven extracellular proteases was used to produce human mast cell chymase and is a viable expression system for serine proteases and other classes of proteins. Chymase is produced at 0.3–0.5 mg/l and is purified by three chromatography steps. Two crystal forms of PMSF-treated chymase were optimized. The first is C2 with a=47.94 Å, b=85.23 Å, c=174.18 Å, β=96.74°, and diffracts to at least 2.1 Å, while the second is P212121, with cell dimensions a=43.93 Å, b=58.16 Å, and c=86.09 Å, and a diffraction limit of approximately 1.9 Å. The first crystal form has either three or four molecules/asymmetric unit, while the second has one molecule/asymmetric unit.