Amonabactin: a family of novel siderophores from a pathogenic bacterium

 Four peptide-based bis-catecholate siderophores, collectively known as the amonabactins, have been isolated from Aeromonas hydrophila. They have been fully characterized: tandem mass spectroscopy established the sequence of the amino acid components, chiral gas chromatographic mass spectra established the amino acid chirality, and two-dimensional NMR techniques determined the full connectivity and structure. Each of the amonabactins was synthesized and the synthetic material was compared to the natural product as a final proof of structure. These siderophores are bis-catecholates with the backbone composed of either tri- or tetrapeptides in the sequence (gly)-(L)-lys-(L)-lys-(D)-aro, where glycine is the optional amino acid attached to the N^ε of the N terminus lysine and aro is either tryptophan or phenylalanine. The ligand units, 2,3-dihydroxybenzamide groups, are attached to the N^ε amine of the C terminus lysine and either to glycine, if present, or to N^ε amines of the N terminus lysine. Each of the amonabactins supports growth of the organism under low-iron conditions in vitro and in serum. The architecture of these siderophores includes an inverted aromatic amino acid and unusual linkages which should prevent enzymatic hydrolysis of the peptide backbones. This, along with their ability to successfully compete for iron in serum, suggests a role in the pathogenicity of the organism. This paper is number 62 in the series Coordination Chemistry of Microbial Ion Transport. Details of the previous paper are given in [1]. Received: 6 June 1997 / Accepted: 9 September 1997