Fluorescence signaling of ligand binding and assembly in metal-chelating lipid membranes.
BACKGROUND
Chemical information is sometimes transmitted across cell membranes by ligand-induced assembly of receptors. We have previously designed a series of lipids with metal-chelating headgroups that can serve as general receptors for proteins containing accessible histidines. Such lipids can also be derivatized with pyrene, a fluorescent probe that has a different emission maximum when it is aggregated (excimer fluorescence) from that seen for the monomer. We set out to examine whether lipids of this kind would produce a signal in response to ligand binding.


RESULTS
A model ligand, poly-L-histidine (poly(His)), bound specifically to pyrene-labeled Cu(II)-iminodiacetate lipid (Cu-PSIDA) within a membrane matrix. Binding of poly(His) induces the redistribution of Cu-PSIDA, so that it forms pyrene-rich domains that are detectable by the increased ratio of excimer to monomer fluorescence. Using rhodamine-labeled poly(His), we have shown that the receptor lipid domains correspond to poly(His)-rich domains below the lipid interface.


CONCLUSIONS
The Cu-PSIDA receptor signals binding of the macromolecular ligand through its excimer fluorescence and allows the resulting domains formed by ligand assembly to be imaged. Fluorescent Cu-PSIDA can thus serve as an optical reporter of ligand-induced lipid reorganization.
Maloney
K
K
Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology, Pasadena, CA 91125, USA. frances@macpost.caltech.edu
Shnek
D
D
Sasaki
D
D
Arnold
F
F
D002614:Chelating Agents / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008856:Microscopy, Fluorescence
D002614:Chelating Agents; D005456:Fluorescent Dyes; D008051:Lipid Bilayers