A Bidomain Nonribosomal Peptide Synthetase Encoded by FUM14 Catalyzes the Formation of Tricarballylic Esters in the Biosynthesis of Fumonisins

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• 作者：Kathia Zaleta-Rivera ; Chunping Xu ; Fengan Yu ; Robert A. E. Butchko ; Robert H. Proctor ; Marí ; a E. Hidalgo-Lara ; Ashraf Raza ; Patrick H. Dussault ; and Liangcheng Du
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：February 28, 2006
• 年：2006
• 卷：45
• 期：8
• 页码：2561 - 2569
• 全文大小：245K
• 年卷期：v.45,no.8(February 28, 2006)
• ISSN：1520-4995

文摘

Fumonisins are a group of polyketide-derived mycotoxins produced by Fusarium verticillioides,a filamentous fungus infecting corn and contaminating food and feeds. Fumonisins contain two tricarballylicesters that are critical for toxicity. Here, we present genetic and biochemical data for the esterificationmechanism. FUM14 in F. verticillioides has been deleted by homologous recombination, and the resultantmutant lost the ability to produce fumonisins. Two new metabolites, HFB₃ and HFB₄, which are biosyntheticprecursors of fumonisins lacking the tricarballylic esters, were detected in the mutant. The results suggestthat FUM14 is required for the esterification of fumonisins. FUM14 was predicted to encode a nonribosomalpeptide synthetase (NRPS) containing two domains, peptidyl carrier protein and condensation domain.Both the intact Fum14p and the condensation domain have been expressed in Escherichia coli and purifiedfor activity assays. Fum14p was able to convert HFB₃ and HFB₄ to the tricarballylic esters-containingfumonisins, FB₃ and FB₄, respectively, when incubated with tricarballylic thioester of N-acetylcysteamine.In addition, the condensation domain was able to convert HFB₁ to FB₁. These data provide direct evidencefor the role of Fum14p in the esterification of fumonisins. More interestingly, the results are the firstexample of an NRPS condensation domain catalyzing a C-O bond (ester) formation, instead of the typicalC-N bond (amide) formation in nonribosomal peptides. The understanding of the esterification mechanismprovides useful knowledge for mycotoxin reduction and elimination. The study also provides new insightinto the reactions catalyzed by NRPS.