Molnár I, Aparicio J F, Haydock S F, Khaw L E, Schwecke T, König A, Staunton J, Leadlay P F
Cambridge Centre for Molecular Recognition, Department of Biochemistry, University of Cambridge, UK.
Gene. 1996 Feb 22;169(1):1-7. doi: 10.1016/0378-1119(95)00799-7.
Analysis of the gene cluster from Streptomyces hygroscopicus that governs the biosynthesis of the polyketide immuno-suppressant rapamycin (Rp) has revealed that it contains three exceptionally large open reading frames (ORFs) encoding the modular polyketide synthase (PKS). Between two of these lies a fourth gene (rapP) encoding a pipecolate-incorporating enzyme that probably also catalyzes closure of the macrolide ring. On either side of these very large genes are ranged a total of 22 further ORFs before the limits of the cluster are reached, as judged by the identification of genes clearly encoding unrelated activities. Several of these ORFs appear to encode enzymes that would be required for Rp biosynthesis. These include two cytochrome P-450 monooxygenases (P450s), designated RapJ and RapN, an associated ferredoxin (Fd) RapO, and three potential SAM-dependent O-methyltransferases (MTases), RapI, RapM and RapQ. All of these are likely to be involved in 'late' modification of the macrocycle. The cluster also contains a novel gene (rapL) whose product is proposed to catalyze the formation of the Rp precursor, L-pipecolate, through the cyclodeamination of L-lysine. Adjacent genes have putative roles in Rp regulation and export. The codon usage of the PKS biosynthetic genes is markedly different from that of the flanking genes of the cluster.
对吸水链霉菌中控制聚酮类免疫抑制剂雷帕霉素（Rp）生物合成的基因簇进行分析后发现，该基因簇包含三个异常大的开放阅读框（ORF），编码模块化聚酮合酶（PKS）。在其中两个ORF之间有第四个基因（rapP），编码一种可能还催化大环内酯环闭合的哌啶酸掺入酶。在这些非常大的基因两侧，在达到基因簇边界之前，总共排列着另外22个ORF，这是根据明确编码不相关活性的基因鉴定得出的结论。其中几个ORF似乎编码Rp生物合成所需的酶。这些酶包括两种细胞色素P-450单加氧酶（P450），分别命名为RapJ和RapN，一种相关的铁氧化还原蛋白（Fd）RapO，以及三种潜在的依赖S-腺苷甲硫氨酸的O-甲基转移酶（MTase），即RapI、RapM和RapQ。所有这些酶可能都参与大环的“后期”修饰。该基因簇还包含一个新基因（rapL），其产物被认为通过L-赖氨酸的环脱氨作用催化Rp前体L-哌啶酸的形成。相邻基因在Rp的调控和输出中可能发挥作用。PKS生物合成基因的密码子使用情况与基因簇侧翼基因明显不同。
