title: TonB and the gram-negative dilemma.
abstract: TonB protein serves as an energy transducer to couple cytoplasmic membrane energy to high-affinity active transport of iron siderophores and vitamin B12 across the outer membranes of Gram-negative bacteria. The biochemical mechanism of the energy transduction remains to be determined, but important details are already known. TonB is targeted to and anchored in the cytoplasmic membrane by a single membrane-spanning domain and spans the periplasm to physically interact with outer-membrane receptors of the transport ligands. TonB-dependent energy transduction is modulated by ExbB protein, which stabilizes TonB, and possibly by several other proteins including ExbC, ExbD, and TolQ. TonB has a relatively short functional half-life that is accelerated when rates of active transport across the outer membrane are increased. A model that incorporates this information, as well as some tempered speculation, is presented.
authors: Department of Microbiology, Washington State University, Pullman 99164-4233.
authors: K
authors: K
authors: Postle
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000378:metabolism; D004735:Energy Transfer; D015964:Gene Expression Regulation, Bacterial; D006090:Gram-Negative Bacteria / Q000235:genetics / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D007502:Iron Chelating Agents / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D017262:Siderophores; D014805:Vitamin B 12 / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D007502:Iron Chelating Agents; D008565:Membrane Proteins; D017262:Siderophores; C057616:tonB protein, Bacteria; D007501:Iron; D014805:Vitamin B 12