Selective Removal of Aberrant Extender Units by a Type II Thioesterase for Efficient FR-008/Candicidin Biosynthesis in Streptomyces sp Strain FR-008
Selective Removal of Aberrant Extender Units by a Type II Thioesterase for Efficient FR-008/Candicidin Biosynthesis in Streptomyces sp Strain FR-008
复制标题
通过 II 型硫酯酶选择性去除异常延伸单元以实现链霉菌菌株 FR-008 中高效 FR-008/念珠菌素生物合成
DOI：
10.1128/aem.01012-08
复制
发表时间：
2008-12-01
影响因子：
4.4
通讯作者：
Deng, Zixin
中科院分区：
文献类型：
--
作者：
Zhou, Yongjun;Meng, Qingqing;Deng, Zixin
基因fscTE，编码一个假定的II型硫酯酶（TEII），与FR-008/杀念菌素基因簇。fscTE的缺失减少了约90%的FR-008/杀念菌素的生产，而生产水平得到很好的恢复时，fscTE被添加回突变体中的trans. FscTE是无法补偿的释放的延长的聚酮作为定点灭活的I型硫酯酶（TEI）完全废除FR-008/杀念菌素的生产。FscTE与其来自泰乐菌素生物合成途径的同源物TylO平行的直接生物化学分析证明了它们对酰基硫酯的显著偏好（即，丙酰基-S-N-乙酰基半胱胺[SNAC]优于甲基丙二酰基-SNAC和乙酰基-SNAC优于丙二酰基-SNAC），并因此得出结论，TEII可以通过选择性去除与酰基载体蛋白结合的不可延伸残基来维持有效的聚酮化合物生物合成。在野生型菌株中，在强组成型ermE*p启动子下过表达FscTE不会抑制FR-008/杀念菌素形成，这证实了其体内底物特异性。此外，成功的互补fscTE突变体获得与fscTE和tylO，而没有互补检测到与非核糖体肽合成酶（NRPS）TEII tycF和srfAD，反映底物特异性的TEII不同于那些无论是聚酮酶或NRPS。
Gene fscTE, encoding a putative type II thioesterase (TEII), was associated with the FR-008/candicidin gene cluster. Deletion of fscTE reduced approximately 90% of the FR-008/candicidin production, while the production level was well restored when fscTE was added back to the mutant in trans. FscTE was unable to compensate for the release of the maturely elongated polyketide as site-directed inactivation of the type I thioesterase (TEI) totally abolished FR-008/candicidin production. Direct biochemical analysis of FscTE in parallel with its homologue TylO from the tylosin biosynthetic pathway demonstrated their remarkable preferences for acylthioesters (i.e., propionyl-S-N-acetylcysteamine [SNAC] over methylmalonyl-SNAC and acetyl-SNAC over malonyl-SNAC) and thus concluded that TEII could maintain effective polyketide biosynthesis by selectively removing the nonelongatable residues bound to acyl carrier proteins. Overexpression of FscTE under the strong constitutive ermE*p promoter in the wild-type strain did not suppress FR-008/candicidin formation, which confirmed its substrate specificity in vivo. Furthermore, successful complementation of the fscTE mutant was obtained with fscTE and tylO, whereas no complementation was detected with nonribosomal peptide synthetase (NRPS) TEII tycF and srfAD, reflecting substrate specificities of TEIIs distinctive from those of either polyketide synthases or NRPSs.