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Appl Environ Microbiol, February 1998, p. 555-563, Vol. 64, No. 2
Department of Bioengineering,
Received 12 June 1997/Accepted 28 November 1997
We have isolated the genomic and cDNA clones encoding EG III (a
low-molecular-mass endo-
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Molecular Characterization and Heterologous
Expression of the Gene Encoding a Low-Molecular-Mass Endoglucanase
from Trichoderma reesei QM9414
-1,4-glucanase) gene from
Trichoderma reesei QM9414. The nucleotide sequence
of the cDNA fragment was verified to contain a 702-bp open reading
frame that encodes a 234-amino-acid propeptide. The deduced protein
sequence has significant homologies with family H
endo-
-1,4-glucanases. The 16-amino-acid N-terminal sequence was
shown to function as a leader peptide for possible secretion. Northern
blot analysis showed that the EG III gene transcript, with a length of
about 700 bp, was expressed markedly by cellulose but not by glucose.
The protein has been expressed as a mature form in Escherichia
coli and as secreted forms in Saccharomyces
cerevisiae and Schizosaccharomyces pombe under the
control of tac, alcohol dehydrogenase (ADH1),
and human cytomegalovirus promoters, respectively. The S. cerevisiae and Schizosaccharomyces pombe recombinant
strains showed strong cellulolytic activities on agar plates containing
carboxymethyl cellulose. The E. coli strain expressed small
amounts of EG III in an active form and large amounts of EG III in an
inactive form. The molecular masses of the recombinant EG IIIs were
estimated to be 25, 28, and 29 kDa for E. coli, S. cerevisiae, and Schizosaccharomyces pombe,
respectively, by immunoblot analysis following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Parts of the yeast recombinant EG IIIs decreased their molecular masses to 25 kDa after
treatment with endoglycosidase H and
-mannosidase, suggesting that
they are N glycosylated at least partly.
*
Corresponding author. Mailing address: Department of
Bioengineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-21, Japan. Phone: 81 (258) 479407. Fax: 81 (258)
479400. E-mail: yasushi{at}vos.nagaokaut.ac.jp.
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