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Crystal Complex Structures Reveal How Substrate is Bound in the -4 to the +2 Binding Sites of Humicola grisea Cel12A
- Source :
-
Journal of Molecular Biology . Oct2004, Vol. 342 Issue 5, p1505-1517. 13p. - Publication Year :
- 2004
-
Abstract
- As part of an ongoing enzyme discovery program to investigate the properties and catalytic mechanism of glycoside hydrolase family 12 (GH 12) endoglucanases, a GH family that contains several cellulases that are of interest in industrial applications, we have solved four new crystal structures of wild-type Humicola grisea Cel12A in complexes formed by soaking with cellobiose, cellotetraose, cellopentaose, and a thio-linked cellotetraose derivative (G2SG2). These complex structures allow mapping of the non-covalent interactions between the enzyme and the glucosyl chain bound in subsites -4 to +2 of the enzyme, and shed light on the mechanism and function of GH 12 cellulases. The unhydrolysed cellopentaose and the G2SG2 cello-oligomers span the active site of the catalytically active H.grisea Cel12A enzyme, with the pyranoside bound in subsite -1 displaying a skew boat conformation. After soaking in cellotetraose, the cello-oligomer that is found bound in site -4 to -1 contains a β-1,3-linkage between the two cellobiose units in the oligomer, which is believed to have been formed by a transglycosylation reaction that has occurred during the ligand soak of the protein crystals. The close fit of this ligand and the binding sites occupied suggest a novel mixed β-glucanase activity for this enzyme. [Copyright &y& Elsevier]
- Subjects :
- *BINDING sites
*ENZYMES
*CELLULASE
*CRYSTALLOIDS (Botany)
Subjects
Details
- Language :
- English
- ISSN :
- 00222836
- Volume :
- 342
- Issue :
- 5
- Database :
- Academic Search Index
- Journal :
- Journal of Molecular Biology
- Publication Type :
- Academic Journal
- Accession number :
- 14376661
- Full Text :
- https://doi.org/10.1016/j.jmb.2004.07.098