Iron, piracy and conflict on the bacterial high seas: Ferredoxin containing antimicrobial proteins provide insight into a novel virulence related iron acquisition system in Pectobacterium — ASN Events
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  2. Session Seven - Poster Session B Including Happy Hour & Trade Display
  3. Iron, piracy and conflict on the bacterial high seas: Ferredoxin containing antimicrobial proteins provide insight into a novel virulence related iron acquisition system in Pectobacterium

Iron, piracy and conflict on the bacterial high seas: Ferredoxin containing antimicrobial proteins provide insight into a novel virulence related iron acquisition system in Pectobacterium (#239)

Rhys Grinter 1 , Inokentijs Josts 1 , Alekander Roszak 1 , Kornelius Zeth 2 , Brian O Smith 1 , Joel J Milner 1 , Olwyn Byron 1 , Daniel Walker 1
  1. University of Glasgow, Glasgow, United Kingdom
  2. Unidad de Biofisica (CSIC-UPV/EHU), Leioa

The pectocins are a class of antimicrobial protein recently discovered in our lab, consisting of a fusion between an enzymatic, cell wall disrupting toxin domain and an iron-containing plant-like ferredoxin. These toxins are produced by the Gram-negative phytopathogen Pectobacterium for intraspecies competition and cross the outer-membrane of their target cells using an unprecedented ‘Trojan-horse’ strategy (1). We show that the plant-like ferredoxin domain of these proteins acts as bait, delivering the toxin domain to the periplasm by parasitising a previously undescribed ferredoxin import system. Further to this discovery, we have utilized these unusual toxins to identify the integral outer membrane protein responsible for ferredoxin import, which we have designated the 'Ferredoxin uptake protein A' (FupA). Additionally, using a genetic approach me have identified the periplasmic protein responsible for the liberation of the ferredoxin iron-sulphur cluster and the inner membrane transporter responsible for its import to the cytoplasm. Pectobacterium, a notorious plant pathogen, utilizes this Fup system to obtain iron from its plant host during infection (2).

In recent unpublished results, we have solved the crystal structure of FupA, showing it to be a 22-stranded β-barrel of the TonB-dependent nutrient receptor family. To complement these data we have utilized a combination of NMR and X-ray crystallography to determine the ferredoxin/FupA binding surface in atomic detail. Further, utilizing a combination of X-ray crystallography, SAXS and molecular dynamics simulations we have solved the structure of pectocin M2, a representative member of these toxins, showing that it is flexible in solution and adopts dimensions compatible with traversing the lumen of FupA (3). These data provide insight into the molecular mechanisms by which the ferredoxin domain individually (or in combination with the toxin domain of the pectocins) is imported through FupA into the periplasm of the cell. Ferredoxin import through FupA is to our knowledge, the first example of protein import by the proteobacteria and represents a hitherto undescribed means by which Gram-negative bacterial pathogens obtain iron from their hosts during infection

  1. Grinter, R., Milner, J., and Walker, D. (2012) Ferredoxin Containing Bacteriocins Suggest a Novel Mechanism of Iron Uptake in Pectobacterium spp. PLoS ONE 7, e33033
  2. Grinter, R., Milner, J., and Walker, D. (2013) Beware of proteins bearing gifts: protein antibiotics that use iron as a Trojan horse. FEMS Microbiol. Lett. 338, 1-9
  3. Grinter, R., Josts, I., Zeth, K., Roszak, A. W., McCaughey, L. C., Cogdell, R. J., Milner, J. J., Kelly, S. M., Byron, O., and Walker, D. (2014) Structure of the atypical bacteriocin pectocin M2 implies a novel mechanism of protein uptake. Mol. Microbiol. 93, 234-246