Patteson Jon B, Cai Wenlong, Johnson Rachel A, Santa Maria Kevin C, Li Bo
Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
Biochemistry. 2018 Jan 9;57(1):61-65. doi: 10.1021/acs.biochem.7b00943. Epub 2017 Nov 7.
Diketopiperazines (DKPs) make up a large group of natural products with diverse structures and biological activities. Bicyclomycin is a broad-spectrum DKP antibiotic with unique structure and function: it contains a highly oxidized bicyclic [4.2.2] ring and is the only known selective inhibitor of the bacterial transcription termination factor, Rho. Here, we identify the biosynthetic gene cluster for bicyclomycin containing six iron-dependent oxidases. We demonstrate that the DKP core is made by a tRNA-dependent cyclodipeptide synthase, and hydroxylations on two unactivated sp carbons are performed by two mononuclear iron, α-ketoglutarate-dependent hydroxylases. Using bioinformatics, we also identify a homologous gene cluster prevalent in a human pathogen Pseudomonas aeruginosa. We detect bicyclomycin by overexpressing this gene cluster and establish P. aeruginosa as a new producer of bicyclomycin. Our work uncovers the biosynthetic pathway for bicyclomycin and sheds light on the intriguing oxidation chemistry that converts a simple DKP into a powerful antibiotic.
二酮哌嗪（DKPs）构成了一大类具有多样结构和生物活性的天然产物。双环霉素是一种具有独特结构和功能的广谱DKP抗生素：它含有一个高度氧化的双环[4.2.2]环，是已知的唯一一种细菌转录终止因子Rho的选择性抑制剂。在此，我们鉴定出了包含六种铁依赖性氧化酶的双环霉素生物合成基因簇。我们证明DKP核心由一种依赖tRNA的环二肽合酶合成，两个未活化的sp碳上的羟基化由两种单核铁、α-酮戊二酸依赖性羟化酶完成。利用生物信息学，我们还鉴定出了在人类病原体铜绿假单胞菌中普遍存在的一个同源基因簇。通过过表达这个基因簇，我们检测到了双环霉素，并将铜绿假单胞菌确立为双环霉素的新产生菌。我们的工作揭示了双环霉素的生物合成途径，并阐明了将一种简单的DKP转化为一种强效抗生素的有趣氧化化学过程。
