The cDNA designated celB from the anaerobic rumen fungus Neocallimastix patriciarum contained a single open reading frame of 1422 bp coding for a protein (CelB) of M(r) 53,070. CelB expressed by Escherichia coli harbouring the full-length gene hydrolysed carboxymethylcellulose in the manner of an endoglucanase, but was most active against barley beta-glucan. It also released reducing sugar from xylan and lichenan, but was inactive against crystalline cellulose, laminarin, mannan, galactan and arabinan. The rate of hydrolysis of cellulo-oligosaccharides by CelB increased with increasing chain length from cellotriose to cellopentaose. The predicted structure of CelB contained features indicative of modular structure. The first 360 residues of CelB constituted a fully functional catalytic domain that was homologous with bacterial endoglucanases belonging to cellulase family A, including five which originate from three different species of anaerobic rumen bacteria. Downstream from this domain, and linked to it by a serine/threonine-rich hinge, was a non-catalytic domain containing short tandem repeats, homologous to the C-terminal repeats contained in xylanase A from the same anaerobic fungus. Unlike previous fungal cellulases, genomic celB was devoid of introns. This lack of introns and the homology of its encoded product with rumen bacterial endoglucanases suggest that acquisition of celB by the fungus may at some stage have involved horizontal gene transfer from a prokaryote to N. particiarum.
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January 1994
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Research Article|
January 15 1994
Intronless celB from the anaerobic fungus Neocallimastix patriciarum encodes a modular family A endoglucanase Available to Purchase
L Zhou;
L Zhou
*Department of Cellular Physiology, AFRC Babraham Institute, Babraham, Cambridge CB2 4AT, U.K.
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G P Xue;
G P Xue
†CSIRO Division of Tropical Crops and Pastures, 306 Carmody Road, St. Lucia, Queensland 3067, Australia
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C G Orpin;
C G Orpin
†CSIRO Division of Tropical Crops and Pastures, 306 Carmody Road, St. Lucia, Queensland 3067, Australia
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G W Black;
G W Black
‡Department of Biological and Nutritional Sciences, University of Newcastle uporT Tyne, Newcastle upon Tyne NE1 7RU, U.K.
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H J Gilbert;
H J Gilbert
‡Department of Biological and Nutritional Sciences, University of Newcastle uporT Tyne, Newcastle upon Tyne NE1 7RU, U.K.
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G P Hazlewood
G P Hazlewood
*Department of Cellular Physiology, AFRC Babraham Institute, Babraham, Cambridge CB2 4AT, U.K.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1994 The Biochemical Society, London
1994
Biochem J (1994) 297 (2): 359–364.
Citation
L Zhou, G P Xue, C G Orpin, G W Black, H J Gilbert, G P Hazlewood; Intronless celB from the anaerobic fungus Neocallimastix patriciarum encodes a modular family A endoglucanase. Biochem J 15 January 1994; 297 (2): 359–364. doi: https://doi.org/10.1042/bj2970359
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