Molecular characterization of staphyloferrin B biosynthesis in Staphylococcus aureus.
Siderophores are iron-scavenging molecules produced by many microbes. In general, they are synthesized using either non-ribosomal peptide synthetase (NRPS) or NRPS-independent siderophore (NIS) pathways. Staphylococcus aureus produces siderophores, of which the structures of staphyloferrin A and staphyloferrin B are known. Recently, the NIS biosynthetic pathway for staphyloferrin A was characterized. Here we show that, in S. aureus, the previously identified sbn (siderophore biosynthesis) locus encodes enzymes required for the synthesis of staphyloferrin B, an alpha-hydroxycarboxylate siderophore comprised of l-2,3-diaminopropionic acid, citric acid, 1,2-diaminoethane and alpha-ketoglutaric acid. Staphyloferrin B NIS biosynthesis was recapitulated in vitro, using purified recombinant Sbn enzymes and the component substrates. In vitro synthesized staphyloferrin B readily promoted the growth of iron-starved S. aureus, via the ABC transporter SirABC. The SbnCEF synthetases and a decarboxylase, SbnH, were necessary and sufficient to produce staphyloferrin B in reactions containing component substrates l-2,3-diaminopropionic acid, citric acid and alpha-ketoglutaric acid. Since 1,2-diaminoethane was not required, this component of the siderophore arises from the SbnH-dependent decarboxylation of a 2,3-diaminoproprionic acid-containing intermediate. Liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analyses of a series of enzyme reactions identified mass ions corresponding to biosynthetic intermediates, allowing for the first proposed biosynthetic pathway for staphyloferrin B.
Cheung
Johnson
J
Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada N6A 5C1.
Beasley
Federico C
FC
Liu
Suya
S
Lajoie
Gilles A
GA
Heinrichs
David E
DE
D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D002951:Citrates / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D019343:Citric Acid / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005029:Ethylenediamines / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D007501:Iron / Q000378:metabolism; D007502:Iron Chelating Agents / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000378:metabolism; D005810:Multigene Family; D009952:Ornithine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D010453:Peptide Synthases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D017262:Siderophores / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism*; D013237:Stereoisomerism; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000378:metabolism
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002951:Citrates; D005029:Ethylenediamines; D005290:Ferric Compounds; D007502:Iron Chelating Agents; D007656:Ketoglutaric Acids; D017262:Siderophores; D015091:beta-Alanine; C083439:staphyloferrin B; C063851:staphyloferrin A; D019343:Citric Acid; C031234:ethylenediamine; C011757:2,3-diaminopropionic acid; D007501:Iron; D009952:Ornithine; D010453:Peptide Synthases