Ramos Angelina, Lombó Felipe, Braña Alfredo F, Rohr Jürgen, Méndez Carmen, Salas José A
Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Universidad de Oviedo, 33006 Oviedo, Spain.
Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 725 Rose Street, Lexington, KY 40536-0082, USA.
Microbiology (Reading). 2008 Mar;154(Pt 3):781-788. doi: 10.1099/mic.0.2007/014035-0.
Elloramycin is an anthracycline-like antitumour drug produced by Streptomyces olivaceus Tü2353. 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.
埃罗霉素是由橄榄色链霉菌Tü2353产生的一种蒽环类抗肿瘤药物。先前已表明黏粒cos16F4可指导埃罗霉素苷元8-去甲基四环素C（8-DMTC）的生物合成，但不能指导埃罗霉素的生物合成。对cos16F4中24.2 kb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开放阅读框。这17个基因编码聚酮化合物部分的生物合成、糖基转移、四环环和糖部分的甲基化以及输出。在橄榄色链霉菌染色体中还鉴定出了4个编码l-鼠李糖生物合成所需酶活性的基因（rhaA、rhaB、rhaC和rhaD）。通过rhaB基因的插入失活证明了该鼠李糖基因簇参与埃罗霉素的生物合成，产生了一个积累8-DMTC苷元的非生产突变体。在淡紫链霉菌中，cos16F4与pEM4RO（表达4个鼠李糖生物合成基因）共表达导致了埃罗霉素的形成，表明这两个亚簇都是埃罗霉素生物合成所必需的。这些结果表明，与大多数放线菌的生物合成基因簇不同，参与埃罗霉素生物合成的基因位于两个染色体位点。
