Crnovčić Ivana, Rückert Christian, Semsary Siamak, Lang Manuel, Kalinowski Jörn, Keller Ullrich
Institut für Chemie, Technische Universität Berlin, Berlin-Charlottenburg.
Technology Platform Genomics, Center for Biotechnology, Bielefeld University, Bielefeld, Germany.
Adv Appl Bioinform Chem. 2017 Apr 7;10:29-46. doi: 10.2147/AABC.S117707. eCollection 2017.
Sequencing the actinomycin () biosynthetic gene cluster of IMRU 3720, which produces actinomycin X (Acm X), revealed 20 genes organized into a highly similar framework as in the bi-armed C biosynthetic gene cluster of but without an attached additional extra arm of orthologues as in the latter. Curiously, the extra arm of the gene cluster turned out to perfectly match the single arm of the gene cluster in the same order of orthologues including the the presence of two pseudogenes, and , encoding a cytochrome P450 and its ferredoxin, respectively. Orthologues of the latter genes were both missing in the principal arm of the C gene cluster. All orthologues of the extra arm showed a G +C-contents different from that of their counterparts in the principal arm. Moreover, the similarities of translation products from the extra arm were all higher to the corresponding translation products of orthologue genes from the gene cluster than to those encoded by the principal arm of their own gene cluster. This suggests that the duplicated structure of the C biosynthetic gene cluster evolved from previous fusion between two one-armed gene clusters each from a different genetic background. However, while and in the extra arm of the C gene cluster are mutated and therefore are non-functional, their orthologues and in the C gene cluster show no defects seemingly encoding active enzymes with functions specific for Acm X biosynthesis. Both biosynthetic gene clusters lack a kynurenine-3-monooxygenase gene necessary for biosynthesis of 3-hydroxy-4-methylanthranilic acid, the building block of the Acm chromophore, which suggests participation of a genome-encoded relevant monooxygenase during Acm biosynthesis in both and .
对产生放线菌素X（Acm X）的IMRU 3720的放线菌素（）生物合成基因簇进行测序，结果显示有20个基因，其组织框架与的双臂C生物合成基因簇高度相似，但不像后者那样有一个附加的直系同源物额外臂。奇怪的是，基因簇的额外臂结果与基因簇的单臂完全匹配，直系同源物顺序相同，包括存在两个假基因，和，分别编码一种细胞色素P450及其铁氧化还原蛋白。后两个基因的直系同源物在C基因簇的主臂中均缺失。额外臂的所有直系同源物的G +C含量与其在主臂中的对应物不同。此外，额外臂翻译产物与基因簇直系同源基因相应翻译产物的相似性均高于其自身基因簇主臂所编码产物的相似性。这表明C生物合成基因簇的重复结构是由先前来自不同遗传背景的两个单臂基因簇融合进化而来。然而，虽然C基因簇额外臂中的和发生了突变，因此无功能，但它们在C基因簇中的直系同源物和似乎没有缺陷，似乎编码对Acm X生物合成具有特定功能的活性酶。两个生物合成基因簇都缺乏3 - 羟基 - 4 - 甲基邻氨基苯甲酸生物合成所需的犬尿氨酸 - 3 - 单加氧酶基因，3 - 羟基 - 4 - 甲基邻氨基苯甲酸是Acm发色团的组成部分，这表明在和的Acm生物合成过程中，基因组编码的相关单加氧酶参与其中。
