title: Mutation of L-2,3-diaminopropionic acid synthase genes blocks staphyloferrin B synthesis in Staphylococcus aureus.
abstract: BACKGROUND
  Staphylococcus aureus synthesizes two siderophores, staphyloferrin A and staphyloferrin B, that promote iron-restricted growth. Previous work on the biosynthesis of staphyloferrin B has focused on the role of the synthetase enzymes, encoded from within the sbnA-I operon, which build the siderophore from the precursor molecules citrate, alpha-ketoglutarate and L-2,3-diaminopropionic acid. However, no information yet exists on several other enzymes, expressed from the biosynthetic cluster, that are thought to be involved in the synthesis of the precursors (or synthetase substrates) themselves.
  
  
  RESULTS
  Using mutants carrying insertions in sbnA and sbnB, we show that these two genes are essential for the synthesis of staphyloferrin B, and that supplementation of the growth medium with L-2,3-diaminopropionic acid can bypass the block in staphyloferrin B synthesis displayed by the mutants. Several mechanisms are proposed for how the enzymes SbnA, with similarity to cysteine synthase enzymes, and SbnB, with similarity to amino acid dehydrogenases and ornithine cyclodeaminases, function together in the synthesis of this unusual nonproteinogenic amino acid L-2,3-diaminopropionic acid.
  
  
  CONCLUSIONS
  Mutation of either sbnA or sbnB result in abrogation of synthesis of staphyloferrin B, a siderophore that contributes to iron-restricted growth of S. aureus. The loss of staphyloferrin B synthesis is due to an inability to synthesize the unusual amino acid L-2,3-diaminopropionic acid which is an important, iron-liganding component of the siderophore structure. It is proposed that SbnA and SbnB function together as an L-Dap synthase in the S. aureus cell.
authors: Department of Microbiology & Immunology, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 5C1, Canada.
authors: Federico C
authors: FC
authors: Beasley
authors: Johnson
authors: J
authors: Cheung
authors: David E
authors: DE
authors: Heinrichs
mesh_terms: D000642:Ammonia-Lyases / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D053898:Biosynthetic Pathways; D002951:Citrates / Q000096:biosynthesis*; D003547:Cysteine Synthase / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D009154:Mutation; D009876:Operon; D013211:Staphylococcus aureus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000096:biosynthesis
chemical_list: D001426:Bacterial Proteins; D002951:Citrates; D015091:beta-Alanine; C083439:staphyloferrin B; C011757:2,3-diaminopropionic acid; D003547:Cysteine Synthase; D000642:Ammonia-Lyases; C021914:ornithine cyclodeaminase