Biosynthesis of the ansamycin antibiotic rifamycin: deductions from the molecular analysis of the rif biosynthetic gene cluster of Amycolatopsis mediterranei S699
Biosynthesis of the ansamycin antibiotic rifamycin: deductions from the molecular analysis of the rif biosynthetic gene cluster of Amycolatopsis mediterranei S699
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DOI：
10.1016/s1074-5521(98)90141-7
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发表时间：
1998-02-01
影响因子：
--
通讯作者：
Floss, HG
中科院分区：
文献类型：
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作者：
August, PR;Tang, L;Floss, HG
背景：安莎霉素类抗生素由多种放线菌产生。它们的碳框架来自聚酮途径，通过使用不寻常的起始单元的聚酮合酶（PKS）。利福霉素（Rifamycin，rif）是由地中海拟无枝酸菌（Amycolatopsis mediterranei）产生的安莎霉素的原型，具有重要的药用价值。虽然它的基本前身（3-氨基-5-羟基苯甲酸AHBA，以及乙酸和丙酸），并鉴定了几种生物合成中间体，但对AHBA的起源知之甚少，也没有对PKS以及修饰初始中间体的各种基因和酶进行表征。通过对来自A.医生。研究了利福霉素B生物合成中某些基因的参与情况。至少有5个基因对AHBA的合成是必需的，5个基因被确定为编码使用AHBA作为起始单元的模块化I型PKS，20个或更多个基因似乎控制聚酮衍生框架的修饰以及利福霉素抗性和输出。还鉴定了推定的调控基因。在rifA的末端破坏PKS基因会破坏利福霉素B的产生，并导致P8/1-OG的形成，P8/1-OG是利福霉素生物合成的一种已知的分流产物，而破坏可能编码脱氧糖生物合成酶的orf 6和orf 9基因则没有明显的影响。介导的是由结构基因、抗性基因和输出基因以及调节基因组成的单个基因簇。本文描述的基因可以被修饰以产生新形式的利福霉素，其可以有效地对抗利福霉素耐药微生物。
Background: The ansamycin class of antibiotics are produced by various Actinomycetes. Their carbon framework arises from the polyketide pathway via a polyketide synthase (PKS) that uses an unusual starter unit. Rifamycin (rif), produced by Amycolatopsis mediterranei, is the archetype ansamycin and it is medically important. Although its basic precursors (3-amino-5-hydroxy benzoic acid AHBA, and acetic and propionic acids) had been established, and several biosynthetic intermediates had been identified, very little was known about the origin of AHBA nor had the PKS and the various genes and enzymes that modify the initial intermediate been characterized.Results: A set of 34 genes clustered around the rifK gene encoding AHBA synthase were defined by sequencing all but 5 kilobases (kb) of a 95 kb contiguous region of DNA from A. mediterranei. The involvement of some of the genes in the biosynthesis of rifamycin B was examined, At least five genes were shown to be essential for the synthesis of AHBA, five genes were determined to encode the modular type I PKS that uses AHBA as the starter unit, and 20 or more genes appear to govern modification of the polyketide-derived framework, and rifamycin resistance and export. Putative regulatory genes were also identified. Disruption of the PKS genes at the end of rifA abolished rifamycin B production and resulted in the formation of P8/1-OG, a known shunt product of rifamycin biosynthesis, whereas disruption of the orf6 and orf9 genes, which may encode deoxysugar biosynthesis enzymes, had no apparent effect.Conclusions: Rifamycin production in A. mediterranei is governed by a single gene cluster consisting of structural, resistance and export, and regulatory genes. The genes characterized here could be modified to produce novel forms of the rifamycins that may be effective against rifamycin-resistant microorganisms.