Identification of the <Emphasis Type="Italic">bkdAB</Emphasis> gene cluster,a plausible source of the starter-unit for virginiamycin M production in <Emphasis Type="Italic">Streptomyces virginiae</Emphasis> |
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Authors: | Nattika Pulsawat Shigeru Kitani Hiroshi Kinoshita Chang Kwon Lee Takuya Nihira |
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Institution: | (1) International Center for Biotechnology, Osaka University, 2-1, Yamadaoka, Suita, Osaka 565-0871, Japan;(2) Present address: Department of Physiology, College of Medicine, Institute of Biomedical Science and Technology, Konkuk University, Danwol-Dong 322, Choongju, 380-701, Republic of Korea;(3) MU-OU Collaborative Research Center for Bioscience and Biotechnology, Faculty of Science, Mahidol University, Rama VI Rd., 10400 Bangkok, Thailand |
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Abstract: | The bkdAB gene cluster, which encodes plausible E1 and E2 components of the branched-chain α-keto acid dehydrogenase (BCDH) complex,
was isolated from Streptomyces virginiae in the vicinity of a regulatory island for virginiamycin production. Gene disruption of bkdA completely abolished the production of virginiamycin M (a polyketide-peptide antibiotic), while the production of virginiamycin
S (a cyclodepsipeptide antibiotic) was unaffected. Complementation of the bkdA disruptant by genome-integration of intact bkdA completely restored the virginiamycin M production, indicating that the bkdAB cluster is essential for virginiamycin M biosynthesis, plausibly via the provision of isobutyryl-CoA as a primer unit. In
contrast to a feature usually seen in the Streptomyces E1 component, namely, the separate encoding of the α and β subunits, S. virginiae
bkdA seemed to encode the fused form of the α and β subunits, which was verified by the actual catalytic activity of the fused
protein in vitro using recombinant BkdA overexpressed in Escherichia coli. Supply of an additional bkdA gene under the strong and constitutive promoter ermE* in the wild-type strain of S. virginiae resulted in enhanced production of virginiamycin M, suggesting that the supply of isobutyryl-CoA is one of the rate-limiting
factors in the biosynthesis of virginiamycin M. |
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Keywords: | Virginiamycin Streptomyces virginiae Branched-chain α -keto acid dehydrogenase |
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