BACTERIAL IRON TRANSPORT - STRUCTURE ELUCIDATION BY FAB-MS AND BY 2D NMR (H-1, C-13, N-15) OF PYOVERDIN G4R, A PEPTIDIC SIDEROPHORE PRODUCED BY A NITROGEN-FIXING STRAIN OF PSEUDOMONAS-PUTIDA

The structures of the pyoverdins excreted in iron-deficient conditions by Pseudomonas putida G4R, a nitrogen-fixing Pseudomonas have been es tablished using FAB-MS and 2D H-1, C-13 & N-15 NMR on both the unlabel led and the N-15-labelled molecules. They are chromopeptides possessin g the following linear heptapeptide: beta-OHAsp-(L)-CTHPMD-Gly-(L)-Ser -(L)-cyclo-OHOrn, bearing a new natural amino acid which is the result of the condensation of one mole of (D) beta-threo-hydroxyaspartic aci d and one mole of (L) 2,4-diaminobutyric acid forming a tetrahydropyri midine ring. (C) 1997 Elsevier Science Ltd.