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Research article - Peer-reviewed, 2003

Cel6A, a major exoglucanase from the cellulosome of the anaerobic fungi Piromyces sp E2 and Piromyces equi

Harhangi HR, Freelove ACJ, Ubhayasekera W, van Dinther M, Steenbakkers PJM, Akhmanova A, van der Drift C, Jetten MSM, Mowbray SL, Gilbert HJ, den Camp HJMO


Anaerobic fungi possess high cellulolytic activities, which are organised in high molecular mass (HMM) complexes. Besides catalytic modules, the cellulolytic enzyme components of these complexes contain non-catalytic modules, known as dockerins, that play a key role in complex assembly. Screening of a genomic and a cDNA library of two Piromyces species resulted in the isolation of two clones containing inserts of 5.5 kb (Piromyces sp. E2) and 1.5 kb (Piromyces equi). Both clones contained the complete coding region of a glycoside hydrolase (GH) from family 6, consisting of a 20 amino acid signal peptide, a 76 (sp. E2)/81 (P. equi) amino acid stretch comprising two fungal noncatalytic docking domains (NCDDs), a 24 (sp. E2)/16 (P. equi) amino acid linker, and a 369 amino acid catalytic module. Homology modelling of the catalytic module strongly suggests that the Piromyces enzymes will be processive cellobiohydrolases. The catalytic residues and all nearby residues are conserved. The reaction is thus expected to proceed via a classical single-displacement (inverting) mechanism that is characteristic of this family of GHs. The enzyme, defined as Cel6A, encoded by the full-length Piromyces E2 sequence was expressed in Escherichia coli. The recombinant protein expressed had a molecular mass of 55 kDa and showed activity against Avicel, supporting the observed relationship of the sequence to those of known cellobiohydrolases. Affinity-purified cellulosomes of Piromyces sp. E2 were analysed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and sodium dodecyl sulfate-polyacrylamide gel (SDS-PAGE) electrophoresis. A major band was detected with the molecular weight of Cel6A. A tryptic fingerprint of this protein confirmed its identity. (C) 2003 Elsevier B.V. All rights reserved

Published in

BBA - Gene Structure and Expression
2003, volume: 1628, number: 1, pages: 30-39

Authors' information

Mowbray, Sherry
Swedish University of Agricultural Sciences, Department of Molecular Biosciences
Ubhayasekera, Wimal
Swedish University of Agricultural Sciences, Department of Molecular Biosciences
Alexander, C J Freelove
Anna, Akhmanova
Chris, van der Drift
Harry, R Harhangi
Harry, J Gilbert
Huub, J M Op den Camp
Maarten, van Dinther
Mike, S M Jetten
Peter, J M Steenbakkers

UKÄ Subject classification

Renewable Bioenergy Research
Animal and Dairy Science
Veterinary Science
Forest Science
Social Sciences
Environmental Sciences related to Agriculture and Land-use
Economics and Business

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