title: Crystal structure of Thermobifida fusca endoglucanase Cel6A in complex with substrate and inhibitor: the role of tyrosine Y73 in substrate ring distortion.
abstract: Endoglucanase Cel6A from Thermobifida fusca hydrolyzes the beta-1,4 linkages in cellulose at accessible points along the polymer. The structure of the catalytic domain of Cel6A from T. fusca in complex with a nonhydrolysable substrate analogue that acts as an inhibitor, methylcellobiosyl-4-thio-beta-cellobioside (Glc(2)-S-Glc(2)), has been determined to 1.5 A resolution. The glycosyl unit in subsite -1 was sterically hindered by Tyr73 and forced into a distorted (2)S(o) conformation. In the enzyme where Tyr73 was mutated to a serine residue, the hindrance was removed and the glycosyl unit in subsite -1 had a relaxed (4)C(1) chair conformation. The relaxed conformation was seen in two complex structures of the mutated enzyme, with cellotetrose (Glc(4)) at 1.64 A and Glc(2)-S-Glc(2) at 1.04 A resolution.
authors.affiliation: Department of Cell and Molecular Biology, University of Uppsala, Biomedical Centre, Box 596, SE-751 24 Uppsala, Sweden.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Larsson
authors.forename: Terese
authors.initials: T
authors.lastname: Bergfors
authors.forename: Elisa
authors.initials: E
authors.lastname: Dultz
authors.forename: Diana C
authors.initials: DC
authors.lastname: Irwin
authors.forename: Annette
authors.initials: A
authors.lastname: Roos
authors.forename: Hugues
authors.initials: H
authors.lastname: Driguez
authors.forename: David B
authors.initials: DB
authors.lastname: Wilson
authors.forename: T Alwyn
authors.initials: TA
authors.lastname: Jones
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D020134:Catalytic Domain; D002475:Cellobiose / Q000737:chemistry; D002480:Cellulase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D002482:Cellulose / Q000031:analogs & derivatives / Q000737:chemistry; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry; D011485:Protein Binding; D013379:Substrate Specificity; D013780:Tetroses / Q000737:chemistry; D014443:Tyrosine
chemical_list: D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D013780:Tetroses; D002475:Cellobiose; C048468:cellotetraose; D014443:Tyrosine; D002482:Cellulose; D002480:Cellulase; C506385:endoglucanase Cel6A, Thermobifida fusca