Iron Release from the Siderophore Pyoverdine in Pseudomonas aeruginosa Involves Three New Actors: FpvC, FpvG, and FpvH
Iron Release from the Siderophore Pyoverdine in Pseudomonas aeruginosa Involves Three New Actors: FpvC, FpvG, and FpvH
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DOI：
10.1021/acschembio.6b01077
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发表时间：
2017-04-01
影响因子：
4
通讯作者：
Schalk, Isabelle J.
中科院分区：
文献类型：
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作者：
Ganne, Geraldine;Brillet, Karl;Schalk, Isabelle J.
铁载体是由细菌产生的铁螯合剂，以获得铁，一种必需的营养素。绿脓菌荧光素（PVDI）是铜绿假单胞菌PAO 1产生的主要铁载体，由一个连接到八肽的荧光发色团组成。PVDI的铁形式通过外膜转运蛋白FpvA从细胞外环境转运到周质中。然后，铁从周质中的铁载体通过不涉及螯合剂的化学修饰而是铁还原步骤的机制释放。在这里，我们通过监测其荧光（因为apo PVDI是荧光的，而PVDI-Fe（III）不是）来跟踪铁从PVDI在体外和活细胞中释放的动力学。内膜蛋白fpvG（PA 2403）和fpvH（PA 2404）的缺失影响Fe-55的摄取通过PVDI和完全废除PVDI-Fe解离，表明这两种蛋白质参与铁的收购通过这个铁载体。使用体外测定的PVDI-Fe解离研究表明，从该铁载体释放铁需要铁还原剂（DTT）和铁螯合剂（亚铁嗪）的存在。在该测定中，DTT可以被内膜蛋白FpvG替代，并且亚铁嗪可以被周质蛋白FpvC替代，这表明在铜绿假单胞菌细胞周质中PVDI-Fe解离的过程中，FpvG充当还原酶，FpvC充当Fe 2+螯合剂。这种从PVDI释放铁的机制在革兰氏阴性菌中是非典型的，但似乎在假单胞菌中是保守的。
Siderophores are iron chelators produced by bacteria to access iron, an essential nutriment. Pyoverdine (PVDI), the major siderophore produced by Pseudomonas aeruginosa PAO1, consists of a fluorescent chromophore linked to an octapeptide. The ferric form of PVDI is transported from the extracellular environment into the periplasm by the outer membrane transporter, FpvA. Iron is then released from the siderophore in the periplasm by a mechanism that does not involve chemical modification of the chelator but an iron reduction step. Here, we followed the kinetics of iron release from PVDI, in vitro and in living cells, by monitoring its fluorescence (as apo PVDI is fluorescent, whereas PVDI-Fe(III) is not). Deletion of the inner membrane proteins fpvG (PA2403) and fpvH (PA2404) affected Fe-55 uptake via PVDI and completely abolished PVDI-Fe dissociation, indicating that these two proteins are involved in iron acquisition via this siderophore. PVDI-Fe dissociation studies, using an in vitro assay, showed that iron release from this siderophore requires the presence of an iron reducer (DTT) and an iron chelator (ferrozine). In this assay, DTT could be replaced by the inner membrane protein, FpvG, and ferrozine by the periplasmic protein, FpvC, suggesting that FpvG acts as a reductase and FpvC as an Fe2+ chelator in the process, of PVDI-Fe dissociation in the periplasm of P. aeruginosa cells. This mechanism of iron release from PVDI is atypical among Gram-negative bacteria but seems to be conserved among Pseudomonads.