Using inverse PCR, two new genes (
btrN and
btrS) were identified upstream of the putative glycosyltransferase gene
btrM in the butirosin-biosynthetic
btr gene cluster of
Bacillus circulans. The upstream gene
btrS showed significant homology with
stsC of
Streptomyces griseus, which encodes L-glutamine:
scyllo-inosose aminotransferase in the biosynthesis of streptomycin. The function of BtrS was further confirmed by heterologous expression in
Escherichia coli and chemical identification of the conversion of 2-deoxy-
scyllo-inosose into 2-deoxy-
scyllo-inosamine. The identification of BtrS as L-glutamine: 2-deoxy-
scyllo-inosose aminotransferase is the first report of the aminotransferase gene responsible for 2-deoxystreptamine biosynthesis.
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