The role of the novel Fem protein VanK in vancomycin resistance in Streptomyces coelicolor.
The non-pathogenic, non-glycopeptide-producing actinomycete Streptomyces coelicolor carries a cluster of seven genes (vanSRJKHAX) that confers inducible, high level resistance to vancomycin. The vanK gene has no counterpart in previously characterized vancomycin resistance clusters, yet vanK is required for vancomycin resistance in S. coelicolor. VanK belongs to the Fem family of enzymes, which add the branch amino acid(s) to the stem pentapeptide of peptidoglycan precursors. Upon exposure to vancomycin, the VanRS two-component system switches on expression of all seven van genes, and the VanHAX enzymes reprogram the cell wall such that precursors terminate D-Ala-D-lactate (Lac) rather than D-Ala-D-Ala, thus conferring resistance to vancomycin, which only binds D-Ala-D-Ala-containing precursors. Here we provide biochemical and genetic evidence that VanK is required for vancomycin resistance because the constitutively expressed FemX enzyme, encoded elsewhere on the chromosome, cannot recognize D-Lac-containing precursors as a substrate, whereas VanK can. Consistent with this view, D-Lac-containing precursors carrying the Gly branch are present in the wild type transiently exposed to vancomycin but are undetectable in a vanK mutant treated in the same way. Further, femX null mutants are viable in the presence of vancomycin but die in its absence. Because only VanK can recognize D-Lac-containing precursors, vancomycin-induced expression of VanHAX in a vanK mutant is lethal, and so vanK is required for vancomycin resistance.
Hong
Hee-Jeon
HJ
Department of Molecular Microbiology, John Innes Centre, Colney, Norwich NR4 7UH, United Kingdom. Hong@bbsrc.ac.uk
Hutchings
Matthew I
MI
Hill
Lionel M
LM
Buttner
Mark J
MJ
D000596:Amino Acids / Q000737:chemistry; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology*; D002473:Cell Wall / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D004351:Drug Resistance; D005838:Genotype; D007773:Lactates; D013058:Mass Spectrometry; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000502:physiology*; D008954:Models, Biological; D008956:Models, Chemical; D005810:Multigene Family; D009154:Mutation; D019884:Nitrogenous Group Transferases / Q000737:chemistry; D009841:Oligonucleotides / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D010457:Peptidoglycan / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D021241:Spectrometry, Mass, Electrospray Ionization; D048372:Streptomyces coelicolor / Q000378:metabolism*; D013997:Time Factors; D014640:Vancomycin / Q000737:chemistry* / Q000494:pharmacology
D000596:Amino Acids; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D007773:Lactates; D026901:Membrane Transport Proteins; D009841:Oligonucleotides; D010455:Peptides; D010457:Peptidoglycan; C119579:VanK protein, Bacillus subtilis; D014640:Vancomycin; D019884:Nitrogenous Group Transferases; C476453:UDP-N-acetylmuramoyl pentapeptide-lysine N(6)-alanyltransferase