Biosynthesis of elloramycin in Streptomyces olivaceus requires glycosylation by enzymes encoded outside the aglycon cluster
Biosynthesis of elloramycin in Streptomyces olivaceus requires glycosylation by enzymes encoded outside the aglycon cluster
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DOI：
10.1099/mic.0.2007/014035-0
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发表时间：
2008-03-01
期刊：
影响因子：
2.8
通讯作者：
Salas, Jose A.
中科院分区：
文献类型：
--
作者：
Ramos, Angelina;Lombo, Felipe;Salas, Jose A.
埃洛霉素是由橄榄色链霉菌Tu 2353产生的蒽环类抗肿瘤药物。Cosmid cos 16 F4以前已被证明可以指导elloramycin糖苷配基8-去甲基四环霉素C（8-DMTC）的生物合成，但不能指导elloramycin。对cos 16 F4中24.2kb插入片段的测序表明，存在17个参与埃罗霉素生物合成的基因（elm基因）以及另外8个可能不参与埃罗霉素生物合成的ORF。这17个基因将编码聚酮部分的生物合成、糖转移、四环和糖部分的甲基化以及输出。同时，还鉴定了4个编码L-鼠李糖生物合成酶活性的基因（rhaA、rhaB、rhaC和rhaD）。橄榄色染色体通过rhaB基因的插入失活，产生积累8-DMTC C糖苷配基的非生产突变体，证明了该鼠李糖基因簇参与埃洛霉素生物合成。cos 16 F4与pEM 4 RO（表达四个鼠李糖生物合成基因）在变铅青链霉菌中的共表达导致了埃洛霉素的形成，表明这两个亚簇都是埃洛霉素生物合成所需的。这些结果表明，与大多数放线菌生物合成基因簇不同，参与埃洛霉素生物合成的基因位于两个染色体位点上。
Elloramycin is an anthracycline-like antitumour drug produced by Streptomyces olivaceus Tu2353. Cosmid cos16F4 has been previously shown to direct the biosynthesis of the elloramycin aglycon 8-demethyltetracenomycin C (8-DMTC), but not elloramycin. Sequencing of the 24.2 kb insert in cos16F4 shows the presence of 17 genes involved in elloramycin biosynthesis (elm genes) together with another additional eight ORFs probably not involved in elloramycin biosynthesis. The 17 genes would code for the biosynthesis of the polyketide moiety, sugar transfer, methylation of the tetracyclic ring and the sugar moiety, and export. Four genes (rhaA, rhaB, rhaC and rhaD) encoding the enzymic activities required for the biosynthesis of the sugar L-rhamnose were also identified in the S. olivaceus chromosome. The involvement of this rhamnose gene cluster in elloramycin biosynthesis was demonstrated by insertional inactivation of the rhaB gene, generating a non-producer mutant that accumulates the 8-DMTC C aglycon. Coexpression of cos16F4 with pEM4RO (expressing the four rhamnose biosynthesis genes) in Streptomyces lividans led to the formation of elloramycin, demonstrating that both subclusters are required for elloramycin biosynthesis. These results demonstrate that, in contrast to most of the biosynthesis gene clusters from actinomycetes, genes involved in the biosynthesis of elloramycin are located in two chromosomal loci.