title: TlpC, a novel chemotaxis protein in Rhodobacter sphaeroides, localizes to a discrete region in the cytoplasm.
abstract: TlpC is encoded in the second chemotaxis operon of Rhodobacter sphaeroides. This protein shows some homology to membrane-spanning chemoreceptors of many bacterial species but, unlike these, is essential for R. sphaeroides chemotaxis to all compounds tested. Genomic replacement of tlpC with a C-terminal gfp fusion demonstrated that TlpC localized to a discrete cluster within the cytoplasm. Immunogold electron microscopy also showed that TlpC localized to a cytoplasmic electron-dense region. Correct TlpC-GFP localization depended on the downstream signalling proteins, CheW3, CheW4 and CheA2, and was tightly linked to cell division. Newly divided cells contained a single cluster but, as the cell cycle progressed, a second cluster appeared close to the initial cluster. As elongation continued, these clusters moved apart so that, on septation, each daughter cell contained a single TlpC cluster. The data presented suggest that TlpC is either a cytoplasmic chemoreceptor responding to or integrating global signals of metabolic state or a novel and essential component of the chemotaxis signalling pathway. These data also suggest that clustering is essential for signalling and that a mechanism may exist for targeting and localizing proteins within the bacterial cytoplasm.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors.forename: G H
authors.initials: GH
authors.lastname: Wadhams
authors.forename: A C
authors.initials: AC
authors.lastname: Martin
authors.forename: S L
authors.initials: SL
authors.lastname: Porter
authors.forename: J R
authors.initials: JR
authors.lastname: Maddock
authors.forename: J C
authors.initials: JC
authors.lastname: Mantotta
authors.forename: H M
authors.initials: HM
authors.lastname: King
authors.forename: J P
authors.initials: JP
authors.lastname: Armitage
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002633:Chemotaxis / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism*; D017353:Gene Deletion; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C089936:TlpC protein, Bacillus subtilis; D049452:Green Fluorescent Proteins