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Microbial iron transport via a siderophore shuttle: A membrane ion transport paradigm

2000; National Academy of Sciences; Volume: 97; Issue: 20 Linguagem: Inglês

10.1073/pnas.200318797

1091-6490

Alain Stintzi, Carmen Barnes, Jide Xu, Kenneth N. Raymond,

Lipid Membrane Structure and Behavior

A mechanism of ion transport across membranes is reported. Microbial transport of Fe 3+ generally delivers iron, a growth-limiting nutrient, to cells via highly specific siderophore-mediated transport systems. In contrast, iron transport in the fresh water bacterium Aeromonas hydrophila is found to occur by means of an indiscriminant siderophore transport system composed of a single multifunctional receptor. It is shown that ( i ) the siderophore and Fe 3+ enter the bacterium together, ( ii ) a ligand exchange step occurs in the course of the transport, and ( iii ) a redox process is not involved in iron exchange. To the best of our knowledge, there have been no other reports of a ligand exchange mechanism in bacterial iron transport. The ligand exchange step occurs at the cell surface and involves the exchange of iron from a ferric siderophore to an iron-free siderophore already bound to the receptor. This ligand exchange mechanism is also found in Escherichia coli and seems likely to be widely distributed among microorganisms.