Bacterial iron acquisition mediated by outer membrane translocation and cleavage of a host protein

Mosbahi, K., Wojnowska, M., Albalat, A. and Walker, D. (2018) Bacterial iron acquisition mediated by outer membrane translocation and cleavage of a host protein. Proceedings of the National Academy of Sciences of the United States of America, 115(26), pp. 6840-6845. (doi:10.1073/pnas.1800672115) (PMID:29891657) (PMCID:PMC6042079)

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Abstract

Iron is an essential micronutrient for most bacteria and is obtained from iron-chelating siderophores or directly from iron-containing host proteins. For Gram-negative bacteria, classical iron transport systems consist of an outer membrane receptor, a periplasmic binding protein, and an inner membrane ABC transporter, which work in concert to deliver iron from the cell surface to the cytoplasm. We recently showed that Pectobacterium spp. are able to acquire iron from ferredoxin, a small and stable 2Fe-2S iron sulfur cluster containing protein and identified the ferredoxin receptor, FusA, a TonB-dependent receptor that binds ferredoxin on the cell surface. The genetic context of fusA suggests an atypical iron acquisition system, lacking a periplasmic binding protein, although the mechanism through which iron is extracted from the captured ferredoxin has remained unknown. Here we show that FusC, an M16 family protease, displays a highly targeted proteolytic activity against plant ferredoxin, and that growth enhancement of Pectobacterium due to iron acquisition from ferredoxin is FusC-dependent. The periplasmic location of FusC indicates a mechanism in which ferredoxin is imported into the periplasm via FusA before cleavage by FusC, as confirmed by the uptake and accumulation of ferredoxin in the periplasm in a strain lacking fusC. The existence of homologous uptake systems in a range of pathogenic bacteria suggests that protein uptake for nutrient acquisition may be widespread in bacteria and shows that, similar to their endosymbiotic descendants mitochondria and chloroplasts, bacteria produce dedicated protein import systems.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Walker, Professor Daniel and Wojnowska, Marta and Mosbahi, Dr Khedidja and Albalat, Dr Amaya
Authors: Mosbahi, K., Wojnowska, M., Albalat, A., and Walker, D.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
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:0027-8424
ISSN (Online):1091-6490
Published Online:11 June 2018
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in PNAS 115(26):6840-6845
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
650711A novel mechanism of protein uptake in Gram-negative bacteriaDaniel WalkerBiotechnology and Biological Sciences Research Council (BBSRC)BB/L02022X/1III - BACTERIOLOGY