UBC Theses and Dissertations
Characterisation of substrate preference in staphylococcus aureus siderophore biosynthesis Kolesnikov, Maxim
Staphylococcus aureus is a common opportunistic pathogen and commensal resident of a majority proportion of the adult population. Emerging drug-resistant and hypervirulent strains such as methicillin-resistant S. aureus (MRSA) have reduced the efficacy of existing treatment options. Iron acquisition from the host is required for the establishment of infection. S. aureus possesses several mechanisms for iron acquisition, including the ferric-iron binding siderophores staphyloferrin A (SA) and staphyloferrin B (SB). To explore the substrate preference of the SA and SB biosynthetic enzymes, crystal structures of biosynthetic enzymes were solved, and alternative substrates were tested. Crystal structures of the synthetases SfaD and SbnF were solved and compared to homologs from other species to define structural determinants of substrate preference. An analogue of SA, substituting D-lysine for D-ornithine during synthesis was produced in vitro and characterized using liquid chromatography and mass spectrometry. Furthermore, S. aureus was shown to be able to use this SA analogue for iron acquisition. Analogues of intermediates in the SB biosynthesis pathways were produced in vitro. The biosynthesis of a functional S. aureus siderophore analogue provided insights into the structures and substrate specificities of siderophore synthesis proteins. The modified siderophores may be of use to deliver antimicrobials into the cell or as a diagnostic for S. aureus infection.
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