Crystal structure of Thermobifida fusca endoglucanase Cel6A in complex with substrate and inhibitor: the role of tyrosine Y73 in substrate ring distortion.
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.
Larsson
Anna M
AM
Department of Cell and Molecular Biology, University of Uppsala, Biomedical Centre, Box 596, SE-751 24 Uppsala, Sweden.
Bergfors
Terese
T
Dultz
Elisa
E
Irwin
Diana C
DC
Roos
Annette
A
Driguez
Hugues
H
Wilson
David B
DB
Jones
T Alwyn
TA
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
D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D013780:Tetroses; D002475:Cellobiose; C048468:cellotetraose; D014443:Tyrosine; D002482:Cellulose; D002480:Cellulase; C506385:endoglucanase Cel6A, Thermobifida fusca