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TlpC, a novel chemotaxis protein in Rhodobacter sphaeroides , localizes to a discrete region in the cytoplasm
Author(s) -
Wadhams G. H.,
Martin A. C.,
Porter S. L.,
Maddock J. R.,
Mantotta J. C.,
King H. M.,
Armitage J. P.
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.03252.x
Subject(s) - biology , cytoplasm , rhodobacter sphaeroides , chemotaxis , microbiology and biotechnology , operon , genetics , gene , bacteria , receptor , mutant
Summary 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, CheW 3 , CheW 4 and CheA 2 , 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.