Structure determination of a siderophore peucechelin from Streptomyces peucetius

Previously, Park et al. isolated a new siderophore from Streptomyces peucetius ATCC 27952 based on information of the genome sequence and the structure of the siderophore was deduced to be a cyclic peptide based on MS/MS analysis. To clarify the structure of the siderophore, we cultured S. peucetius with iron deficient medium. Through several chromatographic procedures, the siderophore named peucechelin was isolated with the yield enough to perform NMR experiments. The planar structure of peucechelin was elucidated by the combination of ESI-MS experiment and NMR spectroscopic analyses of the gallium (III) complex. Unlike the previously deduced cyclic structure, the structure was determined to be a linear peptide which was similar to a known siderophore foroxymithine. The stereochemistries of amino acids constituting peucechelin were determined by applying modified Marfey method to the hydrolysate. Since the biosynthetic gene of peucechelin was formerly determined by Park et al. the similar genes were searched using genome data of other streptomycetes. As a result, the similar genes were found in the genome data of S. venezuelae and S. purpureus. Isolation and identification of siderophore was performed from the iron deficient culture of S. venezuelae. The siderophore of S. venezuelae was identified to be known compound foroxymithine by analysis ESI-MS and NMR spectra in the similar manner with peucechelin. Production of foroxymithine was also observed in the iron deficient culture of S. purpureus. Based on the genome data, comparison of the biosynthetic genes of structurally related siderophores peucechelin and foroxymithine was accomplished in discussion.