PDF(Pubmed)
Abstract：
Microbes synthesize and secrete siderophores, that bind and solubilize precipitated or otherwise unavailable iron in their microenvironments. Gram (-) bacterial TonB-dependent outer membrane receptors capture the resulting ferric siderophores to begin the uptake process. From their similarity to fepA, the structural gene for the Escherichia coli ferric enterobactin (FeEnt) receptor, we identified four homologous genes in the human and animal ESKAPE pathogen Klebsiella pneumoniae (strain Kp52.145). One locus encodes IroN (locus 0027 on plasmid pII), and three other loci encode other FepA orthologs/paralogs (chromosomal loci 1658, 2380, and 4984). Based on the crystal structure of E. coli FepA (1FEP), we modeled the tertiary structures of the K. pneumoniae FepA homologs and genetically engineered individual Cys substitutions in their predicted surface loops. We subjected bacteria expressing the Cys mutant proteins to modification with extrinsic fluorescein maleimide (FM) and used the resulting fluorescently labeled cells to spectroscopically monitor the binding and transport of catecholate ferric siderophores by the four different receptors. The FM-modified FepA homologs were nanosensors that defined the ferric catecholate uptake pathways in pathogenic strains of K. pneumoniae. In Kp52.145, loci 1658 and 4984 encoded receptors that primarily recognized and transported FeEnt; locus 0027 produced a receptor that principally bound and transported FeEnt and glucosylated FeEnt (FeGEnt); locus 2380 encoded a protein that bound ferric catecholate compounds but did not detectably transport them. The sensors also characterized the uptake of iron complexes, including FeGEnt, by the hypervirulent, hypermucoviscous K. pneumoniae strain hvKp1.
Both commensal and pathogenic bacteria produce small organic chelators, called siderophores, that avidly bind iron and increase its bioavailability. Klebsiella pneumoniae variably produces four siderophores that antagonize host iron sequestration: enterobactin, glucosylated enterobactin (also termed salmochelin), aerobactin, and yersiniabactin, which promote colonization of different host tissues. Abundant evidence links bacterial iron acquisition to virulence and infectious diseases. The data we report explain the recognition and transport of ferric catecholates and other siderophores, which are crucial to iron acquisition by K. pneumoniae.
Both commensal and pathogenic bacteria produce small organic chelators, called siderophores, that avidly bind iron and increase its bioavailability. Klebsiella pneumoniae variably produces four siderophores that antagonize host iron sequestration: enterobactin, glucosylated enterobactin (also termed salmochelin), aerobactin, and yersiniabactin, which promote colonization of different host tissues. Abundant evidence links bacterial iron acquisition to virulence and infectious diseases. The data we report explain the recognition and transport of ferric catecholates and other siderophores, which are crucial to iron acquisition by K. pneumoniae.
摘要：
微生物合成和分泌铁载体，在其微环境中结合并溶解沉淀的或以其他方式不可用的铁。革兰氏(-)细菌TonB依赖性外膜受体捕获所产生的铁铁载体以开始摄取过程。从它们与fepA的相似性来看，大肠杆菌铁肠杆菌素（FeEnt）受体的结构基因，我们在人和动物ESKAPE病原体肺炎克雷伯菌（菌株Kp52.145）中鉴定了四个同源基因。一个基因座编码IroN（质粒pII上的基因座0027），和三个其他基因座编码其他FepA直向同源物/旁系同源物(染色体基因座1658、2380和4984)。基于大肠杆菌FepA(1FEP)的晶体结构,我们对肺炎克雷伯菌FepA同源物的三级结构进行了建模,并对其预测的表面环中的单个Cys取代进行了基因工程改造.我们对表达Cys突变蛋白的细菌进行了外源荧光素马来酰亚胺（FM）修饰，并使用所得的荧光标记细胞通过光谱监测四种不同受体对儿茶酚铁铁载体的结合和转运。FM修饰的FepA同源物是定义肺炎克雷伯菌致病菌株中儿茶酚酸铁摄取途径的纳米传感器。在Kp52.145中，基因座1658和4984编码主要识别和运输FeEnt的受体；基因座0027产生主要结合和运输FeEnt和糖基化FeEnt（FeGEnt）的受体；基因座2380编码一种与儿茶酚铁化合物结合的蛋白质，但无法检测到它们的运输。传感器还表征了铁络合物的摄取，包括FeGEnt,通过高毒力，高粘膜粘性肺炎克雷伯菌hvKp1。
目的：共生菌和致病菌均产生少量有机螯合剂，叫做铁载体，强烈结合铁并增加其生物利用度。肺炎克雷伯菌可变地产生四种拮抗宿主铁隔离的铁载体：肠杆菌素，葡糖化肠杆菌素（也称为salmochelin），aerobactin,和Yersiniabactin,促进不同宿主组织的定植。大量证据表明细菌铁的获取与毒力和传染病有关。我们报告的数据解释了儿茶酚铁和其他铁载体的识别和运输，这对肺炎克雷伯菌获得铁至关重要。
目的：共生菌和致病菌均产生少量有机螯合剂，叫做铁载体，强烈结合铁并增加其生物利用度。肺炎克雷伯菌可变地产生四种拮抗宿主铁隔离的铁载体：肠杆菌素，葡糖化肠杆菌素（也称为salmochelin），aerobactin,和Yersiniabactin,促进不同宿主组织的定植。大量证据表明细菌铁的获取与毒力和传染病有关。我们报告的数据解释了儿茶酚铁和其他铁载体的识别和运输，这对肺炎克雷伯菌获得铁至关重要。
