• glycoside hydrolase family 10;
  • xylanases;
  • xylan degradation;
  • TIM-barrel fold.

Xylanases hydrolyze the β-1,4-linked xylose backbone of xylans. They are of increasing interest in the paper and food industries for their pre-bleaching and bio-pulping applications. Such industries demand new xylanases to cover a wider range of cleavage specificity, activity and stability. The catalytic domain of xylanase Xys1 from Streptomyces halstedii JM8 was expressed, purified and crystallized and native data were collected to 1.78 Å resolution with an Rmerge of 4.4%. The crystals belong to space group P212121, with unit-cell parameters a = 34.05, b = 79.60, c = 87.80 Å. The structure was solved by the molecular-replacement method using the structure of the homologue Xyl10A from Streptomyces lividans. In a similar manner to other members of its family, Xys1 folds to form a standard (β/α)8 barrel with the two catalytic functions, the acid/base and the nucleophile, at its C-­terminal side. The overall structure is described and compared with those of related xylanases.