Molecular Structure and Biosynthesis of Pyoverdines Produced by .

This study explored the biosynthetic mechanisms and structural diversity of pyoverdines (PVDs) produced by . Genomic analysis using antiSMASH identified the PVD biosynthetic gene cluster, although the C-terminal peptide sequence could not be predicted. Subsequent liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis revealed the full peptide structure, including modified residues, such as N-acetylhydroxyornithine and cyclohydroxyornithine, and confirmed the presence of several PVD isoforms with different chromophore side chains. Comparative LC-MS analysis across species demonstrated that produces unique PVD molecular mass patterns. The bioinformatic and structural modeling of non-ribosomal peptide synthetase PvdL open reading frame 3 revealed that the A2 and A3 adenylation domains are lysine selective. Although their sequences differ from known lysine-specific signatures, AlphaFold3-based structural prediction revealed conserved substrate-binding configurations, suggesting that similar substrate-binding features may have arisen independently. Notably, Thr, a unique residue in the non-ribosomal code, likely plays a key role in lysine recognition. The high degree of sequence similarity between the A2 and A3 domains may reflect domain duplication and could be involved in the diversification of the PVD structure. Further functional and ecological studies are required to assess the physiological significance of PVDs in microbial iron acquisition.