title: Accumulation of heptaprenyl diphosphate sensitizes Bacillus subtilis to bacitracin: implications for the mechanism of resistance mediated by the BceAB transporter.
abstract: Heptaprenyl diphosphate (C35 -PP) is an isoprenoid intermediate in the synthesis of both menaquinone and the sesquarterpenoids. We demonstrate that inactivation of ytpB, encoding a C35 -PP utilizing enzyme required for sesquarterpenoid synthesis, leads to an increased sensitivity to bacitracin, an antibiotic that binds undecaprenyl pyrophosphate (C55 -PP), a key intermediate in cell wall synthesis. Genetic studies indicate that bacitracin sensitivity is due to accumulation of C35 -PP, rather than the absence of sesquarterpenoids. Sensitivity is accentuated in a ytpB menA double mutant, lacking both known C35 -PP consuming enzymes, and in a ytpB strain overexpressing the HepST enzyme that synthesizes C35 -PP. Conversely, sensitivity in the ytpB background is suppressed by mutation of hepT or by supplementation with 1,4-dihydroxy-2-naphthoate, a co-substrate with C35 -PP for MenA. Bacitracin sensitivity results from impairment of the BceAB and BcrC resistance mechanisms by C35 -PP: in a bceAB bcrC double mutant disruption of ytpB no longer increases bacitracin sensitivity. These results suggest that C35 -PP inhibits both BcrC (a C55 -PP phosphatase) and BceAB (an ABC transporter that confers bacitracin resistance). These findings lead to a model in which BceAB protects against bacitracin by transfer of the target, C55 -PP, rather than the antibiotic across the membrane.
authors.affiliation: Department of Microbiology, Cornell University, Ithaca, NY, 14853-8101, USA.
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Kingston
authors.forename: Heng
authors.initials: H
authors.lastname: Zhao
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Cook
authors.forename: John D
authors.initials: JD
authors.lastname: Helmann
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D001414:Bacitracin / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D024881:Drug Resistance, Bacterial / Q000187:drug effects; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D009154:Mutation; D011106:Polyisoprenyl Phosphates / Q000378:metabolism*; D021381:Protein Transport
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D011106:Polyisoprenyl Phosphates; C000595285:heptaprenyl diphosphate C35; D001414:Bacitracin