Crystallization and preliminary X-ray analysis of Alicyclobacillus acidocaldarius endoglucanase CelA

Crystallization of a family 9 β-1,4-glucanase from the thermoacidophilic bacterium Alicyclobacillus acidocaldarius CelA is reported. Thin plates can be obtained by hanging-drop vapour-diffusion crystallization in high concentrations (60%) of MPD. These crystals are unusual in that they do not bind the dye IZIT in the mother liquor and do not appear to dissolve in water after three weeks or in the storage buffer after 2 d. The crystals diffract weakly and the diffraction pattern is compatible with crystal disorder in one direction. After testing several crystals at the ESRF beamlines ID14-1 and ID14-2, a crystal was found which gave ordered diffraction in all directions. A full data set was collected to 3.0 Å resolution, which allowed unambiguous determination of the space group as P2₁2₁2 and the unit-cell parameters as a = 85, b = 129.7, c = 48.6 Å. Initial promising results from molecular-replacement searches are reported.