kasT gene of Streptomyces kasugaenis M338-M1 encodes a DNA-binding protein which binds to intergenic region of kasU-kasJ in the kasugamycin biosynthesis gene cluster

Abstract

We previously reported that a 4.2 kb 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. 5-15.2 kb 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.