Two new tailoring enzymes, a glycosyltransferase and an oxygenase, involved in biosynthesis of the angucycline antibiotic urdamycin A in Streptomyces fradiae Tu2717
Two new tailoring enzymes, a glycosyltransferase and an oxygenase, involved in biosynthesis of the angucycline antibiotic urdamycin A in Streptomyces fradiae Tu2717
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DOI：
10.1099/00221287-146-1-147
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发表时间：
2000-01-01
期刊：
影响因子：
--
通讯作者：
Bechthold, A
中科院分区：
文献类型：
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作者：
Faust, B;Hoffmeister, D;Bechthold, A
乌尔达霉素A是链霉菌Tu2717的主要产物，是一种含有C-糖基连接的D-橄榄糖的绞股蓝环素类抗生素和抗癌剂。为了扩大对乌尔达霉素A生物合成的认识，作者进一步克隆了乌尔达霉素生物合成基因簇的部分基因。在3.35kb的片段上发现了3个新的ORF(urdK、urdJ和urdO)，在8.05kb的片段上发现了7个新的ORF(urd1、urdM、urdJ2、urdZ1、urdGT2、urdG和urdH)。这些基因的推导产物与转运蛋白(urdJ和urdJ2)、调节基因(UrdK)、还原酶(UrdO)、环化酶(Urd1)和脱氧糖生物合成基因(urdG、urdH和urdO)具有相似性。UrdM的产物与加氧酶(N端序列)和还原酶(C端序列)有显著的序列相似性，而urdGT2的推导氨基酸序列与糖基转移酶相似。针对urdM和urdGT2的功能，进行了靶向基因失活实验。UrdM缺失突变株主要积累雷贝霉素，表明urdM参与了乌尔达霉素A的12b位的氧合作用。缺失urdGT2的突变株产生了乌尔达霉素I、乌尔达霉素J和乌尔达霉素K，而不是乌尔达霉素A。乌尔达霉素I、J和K是缺少C-C连接脱氧糖部分的四环心钠素。因此，UrdGT2必须催化乌尔达霉素生物合成途径中最早的糖基转移步骤，即NDP-D-橄榄糖的C-糖基转移。
Urdamycin A, the principal product of Streptomyces fradiae Tu2717, is an angucycline-type antibiotic and anticancer agent containing C-glycosidically linked D-olivose. To extend knowledge of the biosynthesis of urdamycin A the authors have cloned further parts of the urdamycin biosynthetic gene cluster. Three new ORFs (urdK, urdJ and urdO) were identified on a 3.35 kb fragment, and seven new ORFs (urdL, urdM, urdJ2, urdZ1, urdGT2, urdG and urdH) on an 8.05 kb fragment. The deduced products of these genes show similarities to transporters (urdJ and urdJ2), regulatory genes (urdK), reductases (urdO),cyclases (urdL) and deoxysugar biosynthetic genes (urdG, urdH ana urdO). The product of urdM shows striking sequence similarity to oxygenases (N-terminal sequence) as well as reductases (C-terminal sequence), and the deduced amino acid sequence of urdGT2 resembles those of glycosyltransferases. To the function of urdM and urdGT2, targeted gene inactivation experiments were performed. The resulting urdM deletion mutant strains accumulated predominantly rabelomycin, indicating that UrdM is involved in oxygenation at position 12b of urdamycin A. A mutant in which urdGT2 had been deleted produced urdamycin I, urdamycin J and urdamycin K instead of urdamycin A. Urdamycins I, J and K are tetracyclic angucyclinones lacking a C-C connected deoxysugar moiety. Therefore UrdGT2 must catalyse the earliest glycosyltransfer step in the urdamycin biosynthetic pathway, the C-glycosyltransfer of one NDP-D-olivose.