Identification of a novel cellulose‐binding domain the multidomain 120 kDa xylanase XynA of the hyperthermophilic bacterium Thermotoga maritima
- 1 February 1995
- journal article
- Published by Wiley in Molecular Microbiology
- Vol. 15 (3), 431-444
- https://doi.org/10.1111/j.1365-2958.1995.tb02257.x
Abstract
A segment of Thermotoga maritima strain MSB8 chromosomal DNA was isolated which encodes an endo-1,4-β-D-xylanase, and the nucleotide sequence of the xylanase gene, designated xynA, was determined. With a half-life of about 40 min at 90°C at the optimal pH of 6.2, purified recombinant XynA is one of the most thermostable xylanases known. XynA is a 1059-amino-acid (˜120 kDa) modular enzyme composed of an N-terminal signal peptide and five domains, in the order A1-A2-B-C1-C2. By comparison with other xylanases of family 10 of glycosyl hydrolases, the central ˜340-amino-acid part (domain B) of XynA represents the catalytic domain. The N terminal ˜150-amino-acid repeated domains (A1-A2) have no significant similarity to the C-terminal ˜170-amino-acid repeated domains (C1-C2). Cellulose-binding studies with truncated XynA derivatives and hybrid proteins indicated that the C-terminal repeated domains mediate the binding of XynA to microcrystalline cellulose and that C2 alone can also promote cellulose binding. C1 and C2 did not share amino acid sequence similarity with any other known cellulose-binding domain (CBD) and thus are CBDS of a novel type. Structurally related protein segments which are probably also CBDs were found in other multi-domain xylanolytic enzymes. Deletion of the N-terminal repeated domains or of all the non-catalytic domains resulted In substantially reduced tbermostability while a truncated xylanase derivative lacking the C-terminal tandem repeat was as thermostable as the full-length enzyme. It is argued that the multidomain organization of some enzymes may be one of the strategies adopted by thermophiles to protect their proteins against thermal denaturation.Keywords
This publication has 36 references indexed in Scilit:
- The Acid/Base Catalyst in the Exoglucanase/Xylanase from Cellulomonas fimi Is Glutamic Acid 127: Evidence from Detailed Kinetic Studies of MutantsBiochemistry, 1994
- Evidence for a general role for high‐affinity non‐catalytic cellulose binding domains in microbial plant ceil wall hydroiasesMolecular Microbiology, 1994
- Cloning and characterization of β-galactoside and β-glucoside hydrolysing enzymes of Thermotoga maritimaFEMS Microbiology Letters, 1993
- Purification and characterization of a novel thermostable 4‐α‐glucanotransferase of Thermotoga maritima cloned in Escherichia coliEuropean Journal of Biochemistry, 1992
- The binding of Cellulomonas fimi endoglucanase C (CenC) to cellulose and Sephadex is mediated by the N‐terminal repeatsMolecular Microbiology, 1992
- Protein stability and molecular adaptation to extreme conditonsEuropean Journal of Biochemistry, 1991
- Comparative study of the structure/function relationship of wild‐type and structurally modified maltopentaose‐producing amylaseEuropean Journal of Biochemistry, 1991
- The N‐terminal region of an endoglucanase from Pseudomonas fluorescens subspecies cellulosa constitutes a cellulose‐binding domain that is distinct from the catalytic centreMolecular Microbiology, 1990
- Enzyme Immobilization Using the Cellulose-Binding Domain of a Cellulomonas Fimi ExoglucanaseNature Biotechnology, 1989
- Fusion to an endoglucanase allows alkaline phosphatase to bind to celluloseFEBS Letters, 1989