Overproduction, purification, crystallization and preliminary X-ray characterization of a novel carbohydrate-binding module of endoglucanase Cel5A from Eubacterium cellulosolvens.

The anaerobic cellulolytic rumen bacterium Eubacterium cellulosolvens produces a large array of cellulases and hemicellulases that are responsible for the hydrolysis of plant cell-wall polysaccharides. One of these enzymes, endoglucanase Cel5A, comprises two tandemly repeated novel carbohydrate-binding modules (CBMs) and two catalytic domains belonging to glycoside hydrolase family 5 joined by flexible linker sequences. The novel CBM located at the N-terminus of the endoglucanase has been crystallized. The crystals belonged to the hexagonal space group P6(1)22 and contained a single molecule in the asymmetric unit. The structure of the L-selenomethionine derivative has been solved by a MAD experiment on crystals that diffracted to 1.75 Å resolution.