title: Beware of proteins bearing gifts: protein antibiotics that use iron as a Trojan horse.
abstract: Multicellular organisms limit the availability of free iron to prevent the utilization of this essential nutrient by microbial pathogens. As such, bacterial pathogens possess a variety of mechanisms for obtaining iron from their hosts, including a number of examples of vertebrate pathogens that obtain iron directly from host proteins. Recently, two novel members of the colicin M bacteriocin family were discovered in Pectobacterium that suggest that this phytopathogen possesses such a system. These bacteriocins (pectocin M1 and M2) consist of a cytotoxic domain homologous to that of colicin M fused to a horizontally acquired plant-like ferredoxin. This ferredoxin domain substitutes the portion of colicin M required for receptor binding and translocation, presumably fulfilling this role by parasitizing an existing ferredoxin-based iron acquisition pathway. The ability of susceptible strains of Pectobacterium to utilize plant ferredoxin as an iron source was also demonstrated, providing additional evidence for the existence of such a system. If this hypothesis is correct, it represents the first example of iron piracy directly from a host protein by a phytopathogen and serves as a testament of the flexibility of evolution in creating new bacteriocin specificities.
authors.affiliation: Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
authors.forename: Rhys
authors.initials: R
authors.lastname: Grinter
authors.forename: Joel
authors.initials: J
authors.lastname: Milner
authors.forename: Daniel
authors.initials: D
authors.lastname: Walker
mesh_terms: D003087:Colicins / Q000737:chemistry / Q000378:metabolism*; D005288:Ferredoxins / Q000737:chemistry / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008958:Models, Molecular; D044043:Pectobacterium / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D010935:Plant Diseases / Q000382:microbiology*
chemical_list: D003087:Colicins; D005288:Ferredoxins; D007501:Iron