Single-Molecule Analysis of Chemotactic Signaling in Dictyostelium Cells

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Science  26 Oct 2001:
Vol. 294, Issue 5543, pp. 864-867
DOI: 10.1126/science.1063951

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Single-molecule imaging techniques were used to reveal the binding of individual cyclic adenosine 3′,5′-monophosphate molecules to heterotrimeric guanine nucleotide–binding protein coupled receptors on the surface of living Dictyostelium discoideumcells. The binding sites were uniformly distributed and diffused rapidly in the plane of the membrane. The probabilities of individual association and dissociation events were greater for receptors at the anterior end of the cell. Agonist-induced receptor phosphorylation had little effect on any of the monitored properties, whereas G protein coupling influenced the binding kinetics. These observations illustrate the dynamic properties of receptors involved in gradient sensing and suggest that these may be polarized in chemotactic cells.

  • * To whom correspondence should be addressed. E-mail: ueda{at}

  • Present address: Department of Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.

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