We previously reported that a 4.2kb
SacI-
EcoRI DNA region from
Streptomyces kasugaensis M338-M1, a kasugamycin (KSM) producer, included KSM transporter genes (
kasKLM). As an extension of that study, a 3.7kb
PstI-
SacI DNA region, located at 1.5-5.2kb upstream of
kasK, was cloned and sequenced, revealing three complete open reading frames, designated
kasT, kasU and
kasJ. The
kasJ gene encodes a protein (KasJ) with a conserved dinucleotide (FAD)-binding motif. Homology search for KasJ showed its similarity to NADH: N-amidino-
scyllo-inosamine oxidoreductase (StsB) which is involved in biosynthesis of the streptidine moiety of streptomycin (SM) in
S. griseus. The
kasT gene encodes a DNA-binding protein (KasT), including a helix-turn-helix motif near the center of the sequence. This protein is similar in structure to a pathway-specific activator protein (StrR) that plays a role in regulating the SM biosynthesis gene cluster of
S. griseus. A fusion protein (Trx-KasT) clearly showed DNA binding activity with the intergenic region of
kasU-kasJ, suggesting that KasT is a pathway-specific regulator of the KSM biosynthesis gene cluster.
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