Structural basis for ligand binding and processivity in cellobiohydrolase Cel6A from Humicola insolens.
The enzymatic digestion of cellulose entails intimate involvement of cellobiohydrolases, whose characteristic active-center tunnel contributes to a processive degradation of the polysaccharide. The cellobiohydrolase Cel6A displays an active site within a tunnel formed by two extended loops, which are known to open and close in response to ligand binding. Here we present five structures of wild-type and mutant forms of Cel6A from Humicola insolens in complex with nonhydrolyzable thio-oligosaccharides, at resolutions from 1.7-1.1 A, dissecting the structural accommodation of a processing substrate chain through the active center during hydrolysis. Movement of ligand is facilitated by extensive solvent-mediated interactions and through flexibility in the hydrophobic surfaces provided by a sheath of tryptophan residues.
Varrot
Annabelle
A
Department of Chemistry, University of York, Heslington, Y010 5YW, York, United Kingdom.
Frandsen
Torben P
TP
von Ossowski
Ingemar
I
Boyer
Viviane
V
Cottaz
Sylvain
S
Driguez
Hugues
H
Schülein
Martin
M
Davies
Gideon J
GJ
D001203:Ascomycota / Q000201:enzymology*; D001483:Base Sequence; D002240:Carbohydrate Sequence; D020134:Catalytic Domain; D002482:Cellulose / Q000737:chemistry / Q000378:metabolism; D043366:Cellulose 1,4-beta-Cellobiosidase / Q000378:metabolism*; D003460:Crystallization; D017931:DNA Primers; D008024:Ligands; D008969:Molecular Sequence Data; D011485:Protein Binding
D017931:DNA Primers; D008024:Ligands; D002482:Cellulose; D043366:Cellulose 1,4-beta-Cellobiosidase