Journal of Bacteriology, March 1999, p. 1643-1651, Vol. 181, No. 5
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Department of Animal Sciences, University of Illinois at Urbana-Champaign Urbana, IL 61801, USA
Received 21 August 1998/Accepted 16 December 1998
The manA gene of Thermoanaerobacterium
polysaccharolyticum was cloned in Escherichia coli.
The open reading frame of manA is composed of 3,291 bases
and codes for a preprotein of 1,097 amino acids with an estimated
molecular mass of 119,627 Da. The start codon is preceded by a strong
putative ribosome binding site (TAAGGCGGTG) and a putative
35 (TTCGC) and
10 (TAAAAT) promoter sequence. The ManA
of T. polysaccharolyticum is a modular protein. Sequence
comparison and biochemical analyses demonstrate the presence of an
N-terminal leader peptide, and three other domains in the following
order: a putative mannanase-cellulase catalytic domain, cellulose
binding domains 1 (CBD1) and CBD2, and a surface-layer-like protein
region (SLH-1, SLH-2, and SLH-3). The CBD domains show no sequence
homology to any cellulose binding domain yet reported, hence suggesting
a novel CBD. The duplicated CBDs, which lack a disulfide bridge,
exhibit 69% identity, and their deletion resulted in both failure to
bind to cellulose and an apparent loss of carboxymethyl cellulase and
mannanase activities. At the C-terminal region of the gene are three
repeats of 59, 67, and 56 amino acids which are homologous to conserved
sequences found in the S-layer-associated regions within the xylanases
and cellulases of thermophilic members of the
Bacillus-Clostridium cluster. The ManA of T. polysaccharolyticum, besides being an extremely active enzyme, is
the only mannanase gene cloned which shows this domain structure.
Present address: Department of Molecular Biology, Biomolecular
Engineering Research Institute, 6-2-3 Furuedai, Suita, Osaka 565-0874 Japan.
This article has been cited by other articles:
| Appl. Environ. Microbiol. | Infect. Immun. | Eukaryot. Cell |
|---|---|---|
| Mol. Cell. Biol. | J. Virol. | Microbiol. Mol. Biol. Rev. |
| ALL ASM JOURNALS |