Crystallization and preliminary crystallographic analysis of $endo$ -1,4-$\beta$-xyalanase I from $Aspergillus$ $niger$

A family G xylanase from Aspergillus niger has been crystallized using the vapor-diffusion method. Several crystal forms could be obtained using various sodium salts as precipitants. Three of the crystal forms belong to space groups P21, P212121 and P43 and have cell parameters of approximately a = b = 85.1, c = 113.6 Å and [alpha] = [beta] = [gamma] = 90°. These crystal forms can be converted into one another by flash freezing or macroseeding. A fourth crystal form is cubic (space group P213) with unit-cell axes of a = b = c = 112.3 Å. Data sets for three of the four crystal forms have been collected, extending to a maximum resolution of 2.4 Å. The structures of the monoclinic and orthorhombic crystals have been solved by molecular replacement by combining the crystallographic information of the different crystal forms. Refinement of the orthorhombic crystal form is now in progress