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 th e sequence of the amino acid components, chiral gas chromatographic ma ss spectra established the amino acid chirality, and two-dimensional N MR techniques determined the full connectivity and structure. Each of the amonabactins was synthesized and the synthetic material was compar ed to the natural product as a final proof of structure. These siderop hores are bis-catecholates with the backbone composed of either trior tetrapeptides in the sequence (gly)-(L)-lys-(L)-lys-(D)-aro, where gly cine is the optional amino acid attached to the N-epsilon of the N ter minus lysine and aro is either tryptophan or phenylalanine. The ligand units, 2,3-dihydroxybenzamide groups, are attached to the N-epsilon a mine of the C terminus lysine and either to glycine, if present, or to N-epsilon amines of the N terminus lysine. Each of the amonabactins s upports 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 enzymati c hydrolysis of the peptide backbones. This, along with their ability to successfully compete for iron in serum, suggests a role in the path ogenicity of the organism. This paper is number 62 in the series Coord ination Chemistry of Microbial Ion Transport. Details of the previous paper are given in [1].