Section of Molecular Genetics and Microbiology and Institute of Cellular and Molecular Biology, The University of Texas, Austin, TX 78712, USA.
Mol Microbiol. 2011 Sep;81(6):1446-58. doi: 10.1111/j.1365-2958.2011.07775.x. Epub 2011 Aug 4.
Vibrio cholerae, the causative agent of cholera, has an absolute requirement for iron. It transports the catechol siderophores vibriobactin, which it synthesizes and secretes, and enterobactin. These siderophores are transported across the inner membrane by one of two periplasmic binding protein-dependent ABC transporters, VctPDGC or ViuPDGC. We show here that one of these inner membrane transport systems, VctPDGC, also promotes iron acquisition in the absence of siderophores. Plasmids carrying the vctPDGC genes stimulated growth in both rich and minimal media of a Shigella flexneri mutant that produces no siderophores. vctPDGC also stimulated the growth of an Escherichia coli enterobactin biosynthetic mutant in low iron medium, and this effect did not require feoB, tonB or aroB. A tyrosine to phenylalanine substitution in the periplasmic binding protein VctP did not alter enterobactin transport, but eliminated growth stimulation in the absence of a siderophore. These data suggest that the VctPDGC system has the capacity to transport both catechol siderophores and a siderophore-free iron ligand. We also show that VctPDGC is the previously unidentified siderophore-independent iron transporter in V. cholerae, and this appears to complete the list of iron transport systems in V. cholerae.
霍乱弧菌是霍乱的病原体，它对铁有绝对的需求。它运输合成并分泌的儿茶酚类铁载体 vibriobactin 和 enterobactin。这些铁载体通过两种周质结合蛋白依赖的 ABC 转运体之一 VctPDGC 或 ViuPDGC 穿过内膜进行转运。我们在这里表明，这些内膜转运系统之一 VctPDGC 也可以在没有铁载体的情况下促进铁的摄取。携带 vctPDGC 基因的质粒刺激了不产生铁载体的福氏志贺菌突变体在丰富和最低培养基中的生长。VctPDGC 还刺激了铁载体生物合成突变大肠杆菌在低铁培养基中的生长，而这种效应不需要 feoB、tonB 或 aroB。周质结合蛋白 VctP 中的酪氨酸到苯丙氨酸取代不改变 enterobactin 的运输，但消除了在没有铁载体的情况下的生长刺激。这些数据表明，VctPDGC 系统具有运输儿茶酚类铁载体和无铁载体铁配体的能力。我们还表明，VctPDGC 是霍乱弧菌中以前未识别的铁载体独立铁转运体，这似乎完成了霍乱弧菌铁转运系统的清单。
