Crystallization and preliminary X-ray diffraction study of two complexes of a TAXI-type xylanase inhibitor with glycoside hydrolase family 11 xylanases from Aspergillus niger and Bacillus subtilis

Endo-β-1,4-xylanases hydrolyze arabinoxylan, a major constituent of cereal cell walls, and are nowadays widely used in biotechnological processes. Purified complexes of family 11 xylanases from Aspergillus niger and Bacillus subtilis with TAXI I, a TAXI-type xylanase inhibitor from Triticum aestivum L., were prepared. In both cases the complex was crystallized using the hanging-drop vapour-diffusion method. The needle-like crystals of TAXI I in complex with A. niger xylanase belong to the trigonal space group P3₁ or P3₂, with unit-cell parameters a = b = 88.43, c = 128.99 Å, and diffract to 1.8 Å resolution. TAXI I in complex with B. subtilis xylanase crystallizes in the monoclinic space group C2, with a = 107.89, b = 95.33, c = 66.31 Å, β = 122.24°. Complete data sets were collected for both crystal types using synchrotron radiation.