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首页> 外文期刊>Applied and Environmental Microbiology >Selective Removal of Aberrant Extender Units by a Type II Thioesterase for Efficient FR-008/Candicidin Biosynthesis in Streptomyces sp. Strain FR-008
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Selective Removal of Aberrant Extender Units by a Type II Thioesterase for Efficient FR-008/Candicidin Biosynthesis in Streptomyces sp. Strain FR-008

机译：II型硫酯酶选择性去除链霉菌属菌种中高效FR-008 / Candicidin生物合成的异常延伸单位。菌株FR-008

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摘要

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 acyl-thioesters (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.
机译：编码推定的II型硫酯酶（TEII）的基因fscTE与FR-008 / candicidin基因簇相关。删除fscTE减少了FR-008 / candicidin产量的约90％，而将fscTE反式添加回突变体后，产量水平得到了很好的恢复。 FscTE无法补偿成熟延长的聚酮化合物的释放，因为I型硫酯酶（TEI）的定点灭活完全消除了FR-008 / candicidin的产生。直接FscTE的生物化学分析及其与泰乐菌素生物合成途径中的同系物TylO平行，显示了其对酰基硫酯的显着偏爱（即丙酰基-SN-乙酰半胱胺[SNAC]优于甲基丙二酸-SNAC，乙酰基-SNAC优于丙二酸-SNAC），因此结论认为，TEII可以通过选择性去除与酰基载体蛋白结合的不可伸长的残基来维持有效的聚酮化合物生物合成。在野生型菌株的强组成型ermE * p启动子下FscTE的过表达不能抑制FR-008 / candicidin的形成，这证实了其在体内的底物特异性。此外，用fscTE和tylO成功获得了fscTE突变体的互补，而用非核糖体肽合成酶（NRPS）TEII tycF和srfAD未检测到互补，这反映了TEII的底物特异性不同于聚酮化合物或NRPS。

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