Exploitation of an iron transporter for bacterial protein antibiotic import

White, P. et al. (2017) Exploitation of an iron transporter for bacterial protein antibiotic import. Proceedings of the National Academy of Sciences of the United States of America, 114(45), pp. 12051-12056. (doi:10.1073/pnas.1713741114) (PMID:29078392)

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Abstract

Unlike their descendants, mitochondria and plastids, bacteria do not have dedicated protein import systems. However, paradoxically, import of protein bacteriocins, the mechanisms of which are poorly understood, underpins competition among pathogenic and commensal bacteria alike. Here, using X-ray crystallography, isothermal titration calorimetry, confocal fluorescence microscopy, and in vivo photoactivatable cross-linking of stalled translocation intermediates, we demonstrate how the iron transporter FpvAI in the opportunistic pathogen Pseudomonas aeruginosa is hijacked to translocate the bacteriocin pyocin S2 (pyoS2) across the outer membrane (OM). FpvAI is a TonB-dependent transporter (TBDT) that actively imports the small siderophore ferripyoverdine (Fe-Pvd) by coupling to the proton motive force (PMF) via the inner membrane (IM) protein TonB1. The crystal structure of the N-terminal domain of pyoS2 (pyoS2(NTD)) bound to FpvAI (Kd = 240 pM) reveals that the pyocin mimics Fe-Pvd, inducing the same conformational changes in the receptor. Mimicry leads to fluorescently labeled pyoS2(NTD) being imported into FpvAI-expressing P. aeruginosa cells by a process analogous to that used by bona fide TBDT ligands. PyoS2(NTD) induces unfolding by TonB1 of a force-labile portion of the plug domain that normally occludes the central channel of FpvAI. The pyocin is then dragged through this narrow channel following delivery of its own TonB1-binding epitope to the periplasm. Hence, energized nutrient transporters in bacteria also serve as rudimentary protein import systems, which, in the case of FpvAI, results in a protein antibiotic 60-fold bigger than the transporter's natural substrate being translocated across the OM.

Item Type:Articles
Additional Information:** From PubMed via Jisc Publications Router.
Keywords:Pseudomonas aeruginosa, outer membrane receptor, pyocin, transporter
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Walker, Professor Daniel
Authors: White, P., Joshi, A., Rassam, P., Housden, N. G., Kaminska, R., Goult, J. D., Redfield, C., McCaughey, L. C., Walker, D., Mohammed, S., and Kleanthous, C.
College/School:College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Journal Name:Proceedings of the National Academy of Sciences of the United States of America
Publisher:National Academy of Sciences
ISSN:1091-6490
ISSN (Online):1091-6490
Published Online:25 October 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Proceedings of the National Academy of Sciences of the United States of America 114(45):12051–12056
Publisher Policy:Reproduced under a Creative Commons License

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