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Applied and Environmental Microbiology, September 1999, p. 4099-4107, Vol. 65, No. 9
Department of Microbiology and Evolutionary
Biology,
Received 18 March 1999/Accepted 15 July 1999
Two xylanase-encoding genes, named xyn11A and
xyn10B, were isolated from a genomic library of
Cellulomonas pachnodae by expression in Escherichia
coli. The deduced polypeptide, Xyn11A, consists of 335 amino
acids with a calculated molecular mass of 34,383 Da. Different domains
could be identified in the Xyn11A protein on the basis of homology
searches. Xyn11A contains a catalytic domain belonging to family 11 glycosyl hydrolases and a C-terminal xylan binding domain, which are
separated from the catalytic domain by a typical linker sequence.
Binding studies with native Xyn11A and a truncated derivative of
Xyn11A, lacking the putative binding domain, confirmed the function of
the two domains. The second xylanase, designated Xyn10B, consists of
1,183 amino acids with a calculated molecular mass of 124,136 Da.
Xyn10B also appears to be a modular protein, but typical linker
sequences that separate the different domains were not identified. It
comprises a N-terminal signal peptide followed by a stretch of amino
acids that shows homology to thermostabilizing domains. Downstream of
the latter domain, a catalytic domain specific for family 10 glycosyl
hydrolases was identified. A truncated derivative of Xyn10B bound
tightly to Avicel, which was in accordance with the identified
cellulose binding domain at the C terminus of Xyn10B on the basis of
homology. C. pachnodae, a (hemi)cellulolytic bacterium that
was isolated from the hindgut of herbivorous Pachnoda
marginata larvae, secretes at least two xylanases in the culture
fluid. Although both Xyn11A and Xyn10B had the highest homology to
xylanases from Cellulomonas fimi, distinct differences in
the molecular organizations of the xylanases from the two
Cellulomonas species were identified.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Molecular and Biochemical Characterization of Two
Xylanase-Encoding Genes from Cellulomonas
pachnodae
*
Corresponding author. Mailing address: Department of
Microbiology and Evolutionary Biology, Faculty of Science, University of Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The
Netherlands. Phone: 31 (0)24 3652657. Fax: 31 (0)24 3652830. E-mail:
huubcamp{at}sci.kun.nl.
Applied and Environmental Microbiology, September 1999, p. 4099-4107, Vol. 65, No. 9
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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