O. Gat et al., CLONING AND DNA-SEQUENCE OF THE GENE CODING FOR BACILLUS-STEAROTHERMOPHILUS T-6 XYLANASE, Applied and environmental microbiology, 60(6), 1994, pp. 1889-1896
Bacillus stearothermophilus T-6 produces an extracellular thermostable
xylanase. Affinity-purified polyclonal serum raised against the enzym
e was used to screen a genomic library of B. stearothermophilus T-6 co
nstructed in lambda-EMBL3. Two positive phages were isolated, both con
taining similar 13-kb inserts, and their lysates exhibited xylanase ac
tivity. A 3,696-bp SalI-BamHI fragment containing the xylanase gene wa
s subcloned in Escherichia coli and subsequently sequenced. The open r
eading frame of xylanase T-6 consists of 1,236 bp. On the basis of seq
uence similarity, two possible -10 and -35 regions, a ribosome-binding
site at the 5' end of the gene and a potential transcriptional termin
ation motif at the 3' end of the gene, were identified. From the previ
ously known N-terminal amino acid sequence of xylanase T-6 and the pos
sible ribosome-binding site, a putative 28-amino-acid signal peptide w
as deduced. The mature xylanase T-6 consists of 379 amino acids with a
calculated molecular weight and pI of 43,808 and 6.88, respectively.
Multiple alignment of beta-glycanase amino acid sequences revealed hig
hly conserved regions. Northern (RNA) blot analysis indicated that the
xylanase T-6 transcript is about 1.4 kb and that the induction of thi
s enzyme synthesis by xylose is on the transcriptional level.