1olq
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THE TRICHODERMA REESEI CEL12A P201C MUTANT, STRUCTURE AT 1.7 A RESOLUTION
OverviewOverview
As part of a program to discover improved glycoside hydrolase family 12, (GH 12) endoglucanases, we have extended our previous work on the, structural and biochemical diversity of GH 12 homologs to include the most, stable fungal GH 12 found, Humicola grisea Cel12A. The H. grisea enzyme, was much more stable to irreversible thermal denaturation than the, Trichoderma reesei enzyme. It had an apparent denaturation midpoint (T(m)), of 68.7 degrees C, 14.3 degrees C higher than the T. reesei enzyme. There, are an additional three cysteines found in the H. grisea Cel12A enzyme. To, determine their importance for thermal stability, we constructed three H., grisea Cel12A single mutants in which these cysteines were exchanged with, the corresponding residues in the T. reesei enzyme. We also introduced, these cysteine residues into the T. reesei enzyme. The thermal stability, of these variants was determined. Substitutions at any of the three, positions affected stability, with the largest effect seen in H. grisea, C206P, which has a T(m) 9.1 degrees C lower than that of the wild type., The T. reesei cysteine variant that gave the largest increase in, stability, with a T(m) 3.9 degrees C higher than wild type, was the P201C, mutation, the converse of the destabilizing C206P mutation in H. grisea., To help rationalize the results, we have determined the crystal structure, of the H. grisea enzyme and of the most stable T. reesei cysteine variant, P201C. The three cysteines in H. grisea Cel12A play an important role in, the thermal stability of this protein, although they are not involved in a, disulfide bond.
About this StructureAbout this Structure
1OLQ is a Single protein structure of sequence from Hypocrea jecorina with NAG as ligand. Active as Cellulase, with EC number 3.2.1.4 Structure known Active Site: CA1. Full crystallographic information is available from OCA.
ReferenceReference
The Humicola grisea Cel12A enzyme structure at 1.2 A resolution and the impact of its free cysteine residues on thermal stability., Sandgren M, Gualfetti PJ, Paech C, Paech S, Shaw A, Gross LS, Saldajeno M, Berglund GI, Jones TA, Mitchinson C, Protein Sci. 2003 Dec;12(12):2782-93. PMID:14627738
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