Abstract：
The biosynthetic gene clusters (BGCs) for the macrocyclic lactone-based polyketide compounds are extremely large-sized because the polyketide synthases that generate the polyketide chains of the basic backbone are of very high molecular weight. In developing a heterologous expression system for the large BGCs amenable to the production of such natural products, we selected concanamycin as an appropriate target. We obtained a bacterial artificial chromosome (BAC) clone with a 211-kb insert harboring the entire BGC responsible for the biosynthesis of concanamycin. Heterologous expression of this clone in a host strain, Streptomyces avermitilis SUKA32, permitted the production of concanamycin, as well as that of two additional aromatic polyketides. Structural elucidation identified these additional products as ent-gephyromycin and a novel compound that was designated JBIR-157. We describe herein sequencing and expression studies performed on these BGCs, demonstrating the utility of large BAC clones for the heterologous expression of cryptic or near-silent loci.
摘要：
用于基于大环内酯的聚酮化合物的生物合成基因簇(BGC)非常大,因为产生基本主链的聚酮链的聚酮合酶具有非常高的分子量。在开发适合生产此类天然产物的大型BGC的异源表达系统时，我们选择了可卡霉素作为合适的靶点。我们获得了一个具有211kb插入片段的细菌人工染色体（BAC）克隆，其中包含负责伴卡霉素生物合成的整个BGC。该克隆在宿主菌株中的异源表达，阿维链霉菌SUKA32，允许生产可卡霉素，以及两个额外的芳香聚酮。结构阐明将这些另外的产物鉴定为ent-gephyromycin和命名为JBIR-157的新化合物。我们在此描述了对这些BGC进行的测序和表达研究，证明了大型BAC克隆用于异源表达隐蔽或近沉默基因座的实用性。
