Bacterial iron-sulfur (Fe–S) clusters are essential cofactors for many metabolic pathways, and Fe–S cluster-containing proteins (Fe–S proteins) regulate the expression of various important genes. However, biosynthesis of such clusters has remained unknown in genus Burkholderia. Here, we clarified that Burkholderia multivorans ATCC 17616 relies on the ISC system for the biosynthesis of Fe–S clusters, and that the biosynthetic genes are organized as an isc operon, whose first gene encodes IscR, a transcriptional regulatory Fe–S protein. Transcription of the isc operon was repressed and activated under iron-rich and -limiting conditions, respectively, and Fur, an iron-responsive global transcriptional regulator, was indicated to indirectly regulate the expression of isc operon. Further analysis using a ΔiscR mutant in combination with a constitutive expression system of IscR and its derivatives indicated transcriptional repression and activation of isc operon by holo- and apo-forms of IscR, respectively, through their binding to the sequences within an isc promoter-containing (Pisc) fragment. Biochemical analysis using the Pisc fragment suggested that the apo-IscR binding sequence differs from the holo-IscR binding sequence. The results obtained in this study revealed a unique regulatory system for the expression of the ATCC 17616 isc operon that has not been observed in other genera.

细菌铁硫（Fe–S）簇是许多代谢途径中必不可少的辅助因子，含有Fe–S簇的蛋白质（Fe–S蛋白质）调节着各种重要基因的表达。然而，这种簇的生物合成在伯克霍尔德氏菌属中仍然未知。在这里，我们澄清了伯克霍尔德菌（Burkholderia multivorans） ATCC 17616依赖于ISC系统进行Fe–S簇的生物合成，并且该生物合成基因组织为isc操纵子，其第一个基因编码转录调控Fe–S蛋白IscR。ISC的转录操纵子分别在富含铁和限制铁的条件下被抑制和激活，并且表明铁响应的全局转录调节子Fur间接调节isc操纵子的表达。使用Δ进一步分析ISCR组合突变体与ISCR及其衍生物的组成型表达系统表明转录抑制和活化ISC通过holo-和ISCR的脱辅基形式，分别操纵子，通过它们的内结合序列ISC含启动子的（Pisc）片段。使用Pisc片段的生化分析表明，apo-IscR结合序列不同于完整的IscR结合序列。在这项研究中获得的结果揭示了一个独特的调控系统，用于表达ATCC 17616 isc操纵子，这在其他属中都没有观察到。