Mycobacterium bovis aconitase-IRE interactions: integrating iron, oxidative and nitrosative stress responses

牛分枝杆菌是牛结核病的病原体，牛结核病是英国养牛业的主要问题。我们在牛分枝杆菌基因的5‘编码区发现了一个铁反应元件(IRE)，它编码一种必需的细胞壁水解酶。靶信使RNA分子中的IRES被乌头酸酶蛋白(ACN)的脱氧核糖核酸识别，以介导转录后基因的表达。ACN的调节功能是由[4Fe-4S]簇的崩溃触发的，当ACN作为Krebs循环中的一种酶时，[4Fe-4S]簇存在于活性部位，以响应在牛分枝杆菌首选的利基-a肺巨噬细胞中盛行的氧化/亚硝化应激条件。这个项目是基于这样的假设，即牛分枝杆菌ACN是一种触发酶，它参与调节中枢代谢功能和响应巨噬细胞环境的细胞壁重塑的调节电路。虽然真核细胞ACNS在铁稳态调节中的功能已经得到了很好的描述，但细菌ACNS的作用还没有得到充分的研究。细胞壁重塑是结核病发病机制在复制状态和非复制状态之间转换的一个基本特征，这是感染的活跃和潜伏阶段的特征。了解牛分枝杆菌ACN在催化和调节作用之间的转换机制及其在关闭中枢代谢(ACN是分枝杆菌生长所必需的)和重塑细胞壁中所起的作用，将为建立转录后调控在牛分枝杆菌持久性中的意义提供科学基础。

Mycobacterium bovis is the causative agent of bovine TB, a major problem for UK cattle farming. We have identified an iron-responsive element (IRE) in the 5' coding region of an M. bovis gene, which encodes an essential cell wall hydrolase. IREs in target messenger RNA molecules are recognized by the apo-form of aconitase proteins (Acn) to mediate post-transcriptional gene expression. The regulatory function of Acn is triggered by collapse of the [4Fe-4S] cluster, which is present at the active site when Acn acts as an enzyme in the Krebs cycle, in response to the oxidative/nitrosative stress conditions that prevail in M. bovis's preferred niche - a lung macrophage. This project is based on the hypothesis that M. bovis Acn is a trigger enzyme that participates in regulatory circuits linking central metabolic function to cell wall remodeling in response to the macrophage environment.Whilst the function of eukaryotic Acns in regulation of iron homeostasis has been well-characterized, the role of bacterial Acns is understudied. Cell-wall remodeling is a fundamental feature of TB pathogenesis in the transition between replicative and non-replicative states that characterize active and latent stages of infection. Understanding the mechanism of switching between catalytic and regulatory roles of M. bovis Acn and the role this plays in shutting down central metabolism (Acn is essential for mycobacterial growth) and remodeling the cell-wall will provide the scientific underpinning to establish the significance of post-transcriptional regulation in M. bovis persistence.