Modeling ligand-gated receptor activity. FhuA-mediated ferrichrome efflux from lipid vesicles triggered by phage T5

• Published in: The Journal of biological chemistry Vol. 272; no. 3; pp. 1448 - 1451
• Main Authors: Letellier, L, Locher, K P, Plançon, L, Rosenbusch, J P
• Format: Journal Article
• Language: English
• Published: United States 17.01.1997
• Subjects: Bacterial Outer Membrane Proteins - metabolism; Bacteriophages - metabolism; Biological Transport; Escherichia coli; Escherichia coli Proteins; Ferrichrome - metabolism; Ligands; Lipid Metabolism; phage T5; Receptors, Virus - metabolism; Spectrometry, Fluorescence
• DOI: 10.1074/jbc.272.3.1448
• ISSN: 0021-9258

An in vitro assay of iron-ferrichrome translocation across the FhuA protein of outer membranes from Escherichia coli has been devised. Upon reconstitution into large lipid vesicles, bacteriophage T5 binds to this polyvalent receptor, triggering a conformational change that resulted in channel opening. This facilitates the translocation of an iron(III)-siderophore, without the complexities involved in the in vivo process. Efflux of 55Fe(III)-ferrichrome across FhuA channels was determined quantitatively by monitoring the release of trapped radioactivity. The assay is rapid, reliable, and specific, because other bacteriophages, such as Phi80, fail to trigger channel opening of the FhuA receptor.