3wn2
Crystal Structure of Streptomyces coelicolor alpha-L-arabinofuranosidase in complex with xylohexaose
Structural highlights
FunctionEABF_STRCO Involved in the degradation of xylan and is a key enzyme in the complete degradation of the plant cell wall. It has a specific arabinofuranose-debranching activity on xylan from gramineae. Acts synergistically with the xylanases and binds specifically to xylan. From small arabinoxylo-oligosides (ranging from arabinoxylotriose to arabinoxylohexaose), it liberates arabinose and, after prolonged incubation, the purified enzyme exhibits some xylanolytic activity as well (By similarity). Publication Abstract from PubMedalpha-L-arabinofuranosidase, which belongs to the glycoside hydrolase family 62 (GH62), hydrolyzes arabinoxylan but not arabinan or arabinogalactan. The crystal structures of several alpha-L-arabinofuranosidases have been determined, although the structures, catalytic mechanisms, and substrate specificities of GH62 enzymes remain unclear. To evaluate the substrate specificity of a GH62 enzyme, we determined the crystal structure of alpha-L-arabinofuranosidase, which comprises a carbohydrate-binding module family 13 domain at its N terminus and a catalytic domain at its C terminus, from Streptomyces coelicolor. The catalytic domain was a five-bladed beta-propeller consisting of five radially oriented anti-parallel beta-sheets. Sugar complex structures with l-arabinose, xylotriose, and xylohexaose revealed five subsites in the catalytic cleft and an l-arabinose-binding pocket at the bottom of the cleft. The entire structure of this GH62 family enzyme was very similar to that of glycoside hydrolase 43 family enzymes, and the catalytically important acidic residues found in family 43 enzymes were conserved in GH62. Mutagenesis studies revealed that Asp(202) and Glu(361) were catalytic residues, and Trp(270), Tyr(461), and Asn(462) were involved in the substrate-binding site for discriminating the substrate structures. In particular, hydrogen bonding between Asn(462) and xylose at the nonreducing end subsite +2 was important for the higher activity of substituted arabinofuranosyl residues than that for terminal arabinofuranoses. Crystal structure and characterization of the glycoside hydrolase family 62 alpha-L-arabinofuranosidase from Streptomyces coelicolor.,Maehara T, Fujimoto Z, Ichinose H, Michikawa M, Harazono K, Kaneko S J Biol Chem. 2014 Mar 14;289(11):7962-72. doi: 10.1074/jbc.M113.540542. Epub 2014, Jan 30. PMID:24482228[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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