title: The structure of salmochelins: C-glucosylated enterobactins of Salmonella enterica.
abstract: Salmochelins represent novel carbohydrate containing catecholate siderophores, which are excreted by Salmonella enterica and uropathogenic Escherichia coli strains under low-iron stress. While previous analytical data showed salmochelins to contain 2,3-dihydroxybenzoyl-L-serine and glucose, the molecular structure remained elusive. Structure elucidation with electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry (ESI-FTICR-MS), GC-MS and 2D-NMR now revealed that salmochelins are enterobactin-related compounds, which are beta-C-glucosylated at the 5-position of a 2,3-dihydroxybenzoyl residue. The key compound salmochelin S4 is a twofold beta-C-glucosylated enterobactin analogue. Comparison of partial structures of salmochelin with a C-glycosylated compound previously characterized by another group strongly suggest that salmochelins represent the long sought compounds termed Salmonella resistance factors (SRF) or pacifarins. Transformation of iro-genes into enterobactin-producing E. coli K12 confers the ability to produce salmochelins. A detailed analysis proved iroB to be the sole gene with glycosyltransferase activity necessary for salmochelin production. Salmochelins compared to enterobactin are the better siderophores in the presence of serum albumin. This may indicate for salmochelins a considerably more important role for pathogenic processes in certain Escherichia coli and Salmonella infections than formerly assigned to enterobactin. This conclusion is supported by the location of the iro genes on pathogenicity islands of uropathogenic E. coli strains.
authors.affiliation: Institut für Organische Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany.
authors.forename: Bojan
authors.initials: B
authors.lastname: Bister
authors.forename: Daniel
authors.initials: D
authors.lastname: Bischoff
authors.forename: Graeme J
authors.initials: GJ
authors.lastname: Nicholson
authors.forename: Marianne
authors.initials: M
authors.lastname: Valdebenito
authors.forename: Kathrin
authors.initials: K
authors.lastname: Schneider
authors.forename: Günther
authors.initials: G
authors.lastname: Winkelmann
authors.forename: Klaus
authors.initials: K
authors.lastname: Hantke
authors.forename: Roderich D
authors.initials: RD
authors.lastname: Süssmuth
mesh_terms: D002851:Chromatography, High Pressure Liquid; D019992:Databases as Topic; D004758:Enterobactin / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D005798:Genes, Bacterial / Q000235:genetics; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D015394:Molecular Structure; D010088:Oxidoreductases / Q000235:genetics; D019779:Salmonella enterica / Q000737:chemistry* / Q000201:enzymology / Q000235:genetics; D017262:Siderophores / Q000096:biosynthesis / Q000737:chemistry
chemical_list: D017262:Siderophores; D004758:Enterobactin; D010088:Oxidoreductases; C074859:iron oxidase, Thiobacillus ferrooxidans