title: Tryptophan 272: an essential determinant of crystalline cellulose degradation by Trichoderma reesei cellobiohydrolase Cel6A.
abstract: Trichoderma reesei cellobiohydrolase Cel6A (formerly CBHII) has a tunnel shaped active site with four internal subsites for the glucose units. We have predicted an additional ring stacking interaction for a sixth glucose moiety with a tryptophan residue (W272) found on the domain surface. Mutagenesis of this residue selectively impairs the enzyme function on crystalline cellulose but not on soluble or amorphous substrates. Our data shows that W272 forms an additional subsite at the entrance of the active site tunnel and suggests it has a specialised role in crystalline cellulose degradation, possibly in guiding a glucan chain into the tunnel.
authors.affiliation: VTT Biotechnology and Food Research, Espoo, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Koivula
authors.forename: T
authors.initials: T
authors.lastname: Kinnari
authors.forename: V
authors.initials: V
authors.lastname: Harjunpää
authors.forename: L
authors.initials: L
authors.lastname: Ruohonen
authors.forename: A
authors.initials: A
authors.lastname: Teleman
authors.forename: T
authors.initials: T
authors.lastname: Drakenberg
authors.forename: J
authors.initials: J
authors.lastname: Rouvinen
authors.forename: T A
authors.initials: TA
authors.lastname: Jones
authors.forename: T T
authors.initials: TT
authors.lastname: Teeri
mesh_terms: D001665:Binding Sites; D002480:Cellulase / Q000378:metabolism*; D002482:Cellulose / Q000737:chemistry / Q000378:metabolism*; D043366:Cellulose 1,4-beta-Cellobiosidase; D006868:Hydrolysis; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009844:Oligosaccharides / Q000378:metabolism; D014242:Trichoderma / Q000201:enzymology*; D014364:Tryptophan
chemical_list: D009844:Oligosaccharides; D014364:Tryptophan; D002482:Cellulose; D002480:Cellulase; D043366:Cellulose 1,4-beta-Cellobiosidase