X-ray Crystal Structure of Divalent Metal-Activated β-xylosidase, RS223BX
- Source:
- Applied biochemistry and biotechnology 2015 v.177 no.3 pp. 637-648
- ISSN:
- 0273-2289
- Subject:
- X-ray diffraction, histidine, active sites, calcium, cations, divalent metals, glycosides, mutation, xylan 1,4-beta-xylosidase
- Abstract:
- We report the X-ray crystal structure of a glycoside hydrolase family 43 β-xylosidase, RS223BX, which is strongly activated by the addition of divalent metal cations. The 2.69 Å structure reveals that the Ca²⁺ cation is located at the back of the active-site pocket. The Ca²⁺ is held in the active site by the carboxylate of D85, an “extra” acid residue in comparison to other GH43 active sites. The Ca²⁺ is in close contact with a histidine imidazole, which in turn is in contact with the catalytic base (D15) thus providing a mechanism for stabilizing the carboxylate anion of the base and achieve metal activation. The active-site pocket is mirrored by an “inactive-site” pocket of unknown function that resides on the opposite side of the monomer.
- Agid:
- 62506
- Handle:
- 10113/62506
- https://doi.org/10.1007/s12010-015-1767-z