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Applied and Environmental Microbiology, November 1999, p. 4987-4994, Vol. 65, No. 11
National Food Research Institute,
Received 26 April 1999/Accepted 26 August 1999
O-Methyltransferase I catalyzes both the conversion of
demethylsterigmatocystin to sterigmatocystin and the conversion of dihydrodemethylsterigmatocystin to dihydrosterigmatocystin during aflatoxin biosynthesis. In this study, both genomic cloning and cDNA
cloning of the gene encoding O-methyltransferase I were
accomplished by using PCR strategies, such as conventional PCR based on
the N-terminal amino acid sequence of the purified enzyme,
5' and 3' rapid amplification of cDNA ends PCR, and thermal asymmetric interlaced PCR (TAIL-PCR), and genes were sequenced by using
Aspergillus parasiticus NIAH-26. A comparison of the
genomic sequences with the cDNA of the dmtA region revealed
that the coding region is interrupted by three short introns. The cDNA
of the dmtA gene is 1,373 bp long and encodes a
386-amino-acid protein with a deduced molecular weight of 43,023, which
is consistent with the molecular weight of the protein determined by
sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The
C-terminal half of the deduced protein exhibits 76.3% identity with
the coding region of the Aspergillus nidulans StcP protein,
whereas the N-terminal half of dmtA exhibits 73.0%
identity with the 5' flanking region of the stcP gene,
suggesting that translation of the stcP gene may start at a
site upstream from methionine that is different from the site that has
been suggested previously. Also, an examination of the 5' and 3'
flanking regions of the dmtA gene in which TAIL-PCR was
used demonstrated that the dmtA gene is located in the
aflatoxin biosynthesis cluster between (and in the same orientation as)
the omtA and ord-2 genes. Northern blotting
revealed that expression of the dmtA gene is influenced by
both medium composition and culture temperature and that the pattern
correlates with the patterns observed for other genes in the aflatoxin
gene cluster. Furthermore, Southern blotting and PCR analyses of the
dmtA gene showed that a dmtA homolog is present
in Aspergillus oryzae SYS-2.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Cloning and Characterization of the
O-Methyltransferase I Gene (dmtA) from
Aspergillus parasiticus Associated with the Conversions
of Demethylsterigmatocystin to Sterigmatocystin and
Dihydrodemethylsterigmatocystin to Dihydrosterigmatocystin in
Aflatoxin Biosynthesis
*
Corresponding author. Mailing address: National Food
Research Institute, Tsukuba, Ibaraki 305-8642, Japan. Phone:
0298-38-8050. Fax: 0298-38-7996. E-mail:
yabek{at}nfri.affrc.go.jp.
Applied and Environmental Microbiology, November 1999, p. 4987-4994, Vol. 65, No. 11
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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