Identification of the bkdAB gene cluster, a plausible source of the starter-unit for virginiamycin M production in Streptomyces virginiae
Identification of the bkdAB gene cluster, a plausible source of the starter-unit for virginiamycin M production in Streptomyces virginiae
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DOI：
10.1007/s00203-007-0212-2
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发表时间：
2007-06-01
影响因子：
2.8
通讯作者：
Nihira, Takuya
中科院分区：
文献类型：
--
作者：
Pulsawat, Nattika;Kitani, Shigeru;Nihira, Takuya
bkdAB基因簇，它编码合理的E1和E2组分的支链α-酮酸脱氢酶（BCDH）复合物，从弗吉尼亚链霉菌在附近的弗吉尼亚霉素生产的监管岛分离。bkdA的基因破坏完全消除了维吉尼亚霉素M（一种聚酮肽抗生素）的产生，而维吉尼亚霉素S（一种环缩肽抗生素）的产生不受影响。通过完整bkdA的基因组整合来补充bkdA破坏物完全恢复了维吉尼亚霉素M的生产，表明bkdAB簇对于维吉尼亚霉素M的生物合成是必需的，这可能是通过提供异丁酰辅酶A作为引物单元实现的。与通常在链霉菌E1组分中看到的特征，即α和β亚基的单独编码相反，S. virginiae bkdA似乎编码α和β亚基的融合形式，这通过使用在大肠杆菌中过表达的重组BkdA在体外融合蛋白的实际催化活性来验证。在野生型S. virginiae导致弗吉尼亚霉素M的产量增加，表明异丁酰辅酶A的供应是弗吉尼亚霉素M生物合成的限速因素之一。
The bkdAB gene cluster, which encodes plausible E1 and E2 components of the branched-chain alpha-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 alpha and beta subunits, S. virginiae bkdA seemed to encode the fused form of the alpha and beta 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.