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Appl. Environ. Microbiol., 06 1995, 2262-2269, Vol 61, No. 6
DD Morris, RA Reeves, MD Gibbs, DJ Saul and PL Bergquist
The celA, manA, and celB genes from Caldocellulosiruptor saccharolyticus
compose a cellulase-hemicellulase gene cluster and are arranged on a 12-kb
C. saccharolyticus genomic fragment of the recombinant lambda bacteriophage
NZP lambda 2. The beginning of a fourth open reading frame (celC) which was
homologous to the C. saccharolyticus manA and celA genes was located at the
3' end of the 12- kb NZP lambda 2 genomic fragment. Genome-walking PCR was
used to isolate DNA fragments downstream of the C. saccharolyticus celB
gene, and the entire nucleotide sequence of celC was obtained. From the
preliminary nucleotide sequence, celC appeared to encode yet another
multidomain bifunctional enzyme (CelC) consisting of an N-terminal endo-
1,4-beta-D-glucanase domain (75% similar to CelA domain 1), two central
cellulose-binding domains, and a C-terminal endo-1,4-beta-D-mannanase
domain (98% similar to ManA domain 1). However, upon completion of the celC
sequencing, two -1 frameshifts were identified in the region encoding the
putative CelC mannanase domain. The isolated CelC mannanase domain
exhibited no beta-mannanase activity, which supported this observation.
Recombinant PCR was used to correct the celC frameshifts by inserting the
appropriate nucleotides into the gene. The repaired celC fragment
containing the base insertions (manB) expressed strong beta-mannanase
activity on soluble mannan substrates and showed significant activity on
kraft pulp as judged by the release of reducing sugars.
Copyright © 1995, American Society for Microbiology
Correction of the beta-mannanase domain of the celC pseudogene from Caldocellulosiruptor saccharolyticus and activity of the gene product on kraft pulp
Centre for Gene Technology, School of Biological Sciences, University of Auckland, New Zealand.
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