Projects -Fluorescent flagella -Swimming without flagella -Gliding motility -Twitching motility -Fluorescent chemotaxis proteins -Chemotactic signaling studied by FRET -Models of the chemotactic system -Motor force generation -Switching under load

GFP-labeled flagellar motors and TexasRed-labeled flagellar hooks Fluorescent chemotaxis proteins Victor Sourjik constructed a series of strains of E. coli in which components of the chemotaxis machinery, including the flagellar switch, are fused to variants of the green fluorescent protein (a small protein from a jellyfish that crafts its own fluorophore). Most of these strains are motile and chemotactic. For example, a fusion of green fluorescent protein to FliM, a component of the switch, produces cells that display green speckles, as expected if their motor basal bodies are fluorescent. When counter-stained with a red fluorescent anti-hook antibody, every red speckle is paired with a green speckle, but not all green speckles are paired with red ones, as expected: FliM is incorporated early in motor assembly, the hook protein relatively late. Proceeding in this fashion, Victor has shown that the chemotaxis proteins CheY (the signaling molecule that, when phosphorylated, binds to FliM), CheA (the kinase that phosphorylates CheY), and CheZ (a protein that accelerates the dephosphorylaton of CheY-P) tend to cluster at the cell poles, co-localizing with the chemoreceptors (identified by immunofluorescence). This suggests the existence of a signal complex comprising at least four different kinds of proteins (actually five, since a coupling factor, CheW, is known to be associated with CheA). See Miscellaneous movies, GFP labeled motors. Reference Sourjik, V. and Berg, H.C. Location of components of the chemotaxis machinery of Escherichia coli using fluorescent-protein fusions. Molec. Microbiol. 37, 740-751 (2000).

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