title: Purification, crystallization and preliminary X-ray characterization of the pentamodular arabinoxylanase CtXyl5A from Clostridium thermocellum.
abstract: The cellulosome, a highly elaborate extracellular multi-enzyme complex of cellulases and hemicellulases, is responsible for the degradation of plant cell walls. The xylanase CtXyl5A (Cthe_2193) is a multimodular arabinoxylanase which is one of the largest components of the Clostridium thermocellum cellulosome. The N-terminal catalytic domain of CtXyl5A, which is a member of glycoside hydrolase family 5 (GH5), is responsible for the hydrolysis of arabinoxylans. Appended after it are three noncatalytic carbohydrate-binding modules (CBMs), which belong to families 6 (CBM6), 13 (CBM13) and 62 (CBM62). In addition, CtXyl5A has a fibronectin type III-like (Fn3) module preceding the CBM62 and a type I dockerin (DOK) module following it which allows the enzyme to be integrated into the cellulosome through binding to a cohesin module of the protein scaffold CipA. Crystals of the pentamodular enzyme without the DOK module at the C-terminus, with the domain architecture CtGH5-CBM6-CBM13-Fn3-CBM62, have been obtained. The structure of this pentamodular xylanase has been determined by molecular replacement to a resolution of 2.64 Å using coordinates of CtGH5-CBM6, Fn3 and CBM62 from the PDB as search models.
authors.affiliation: CIISA-Faculdade de Medicina Veterinária, Universidade Técnica de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
authors.forename: Joana L A
authors.initials: JL
authors.lastname: Brás
authors.forename: Márcia A S
authors.initials: MA
authors.lastname: Correia
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Romão
authors.forename: José A M
authors.initials: JA
authors.lastname: Prates
authors.forename: Carlos M G A
authors.initials: CM
authors.lastname: Fontes
authors.forename: Shabir
authors.initials: S
authors.lastname: Najmudin
mesh_terms: D048013:Acetivibrio thermocellus / Q000201:enzymology*; D003460:Crystallization; D018360:Crystallography, X-Ray; D014995:Xylosidases / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D014995:Xylosidases; C110296:arabinoxylanase