Discovery of an Iron-Regulated Citrate Synthase in Staphylococcus aureus
Discovery of an Iron-Regulated Citrate Synthase in Staphylococcus aureus
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DOI：
10.1016/j.chembiol.2012.10.003
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发表时间：
2012-12-21
影响因子：
--
通讯作者：
Heinrichs, David E.
中科院分区：
文献类型：
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作者：
Cheung, Johnson;Murphy, Michael E. P.;Heinrichs, David E.
细菌需要从其环境中吸收铁，这对于试图在哺乳动物宿主中生存的细菌病原体同样重要。一个关键的策略是合成称为铁载体的小铁螯合剂。铁载体生物合成系统的研究，在过去的几年里，揭示了新的酶学，因此，已经确定了新的治疗目标。金黄色葡萄球菌，一种著名的人类和动物病原体，产生两种基于柠檬酸盐的铁载体，称为葡萄球菌铁蛋白A和葡萄球菌铁蛋白B。铁调控的葡萄铁蛋白B生物合成的基因簇，sbnA-I，包含几个尚未表征的基因。在这里，我们报告的酶，SbnG，这是注释的基因组序列作为金属依赖性II类醛缩酶的鉴定。与此预测相反，我们报告说，相反，SbnG已演变为催化金属不依赖的柠檬酸合成酶活性，使用草酰乙酸和乙酰辅酶A作为底物。我们描述了一种体外试验，从纯化的酶和底物合成具有生物活性的葡萄球菌铁蛋白B，并确定了几种SbnG抑制剂，包括金属，如钙和镁。
Bacteria need to scavenge iron from their environment, and this is no less important for bacterial pathogens while attempting to survive in the mammalian host. One key strategy is the synthesis of small iron chelators known as siderophores. The study of siderophore biosynthesis systems over the past several years has shed light on novel enzymology and, as such, has identified new therapeutic targets. Staphylococcus aureus, a noted human and animal pathogen, produces two citrate-based siderophores, termed staphyloferrin A and staphyloferrin B. The iron-regulated gene cluster for the biosynthesis of staphyloferrin B, sbnA-I, contains several yet uncharacterized genes. Here, we report on the identification of an enzyme, SbnG, which is annotated in the genome sequence as a metal-dependent class II aldolase. In contrast to this prediction, we report that, instead, SbnG has evolved to catalyze metal-independent citrate synthase activity using oxaloacetate and acetyl-CoA as substrates. We describe an in vitro assay to synthesize biologically active staphyloferrin B from purified enzymes and substrates, and identify several SbnG inhibitors, including metals such as calcium and magnesium.