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Download fileFluorescent Pirenzepine Derivatives as Potential Bitopic Ligands of the Human M1 Muscarinic Receptor
journal contribution
posted on 12.08.2004, 00:00 authored by Chouaib Tahtaoui, Isabelle Parrot, Philippe Klotz, Fabrice Guillier, Jean-Luc Galzi, Marcel Hibert, Brigitte IlienFollowing a recent description of fluorescence resonance energy transfer between enhanced
green fluorescent protein (EGFP)-fused human muscarinic M1 receptors and Bodipy-labeled
pirenzepine, we synthesized seven fluorescent derivatives of this antagonist in order to further
characterize ligand−receptor interactions. These compounds carry Bodipy [558/568], Rhodamine
Red-X [560/580], or Fluorolink Cy3 [550/570] fluorophores connected to pirenzepine through
various linkers. All molecules reversibly bind with high affinity to M1 receptors (radioligand
and energy transfer binding experiments) provided that the linker contains more than six atoms.
The energy transfer efficiency exhibits modest variations among ligands, indicating that the
distance separating EGFP from the fluorophores remains almost constant. This also supports
the notion that the fluorophores may bind to the receptor protein. Kinetic analyses reveal that
the dissociation of two Bodipy derivatives (10 or 12 atom long linkers) is sensitive to the presence
of the allosteric modulator brucine, while that of all other molecules (15−24 atom long linkers)
is not. The data favor the idea that these analogues might interact with both the acetylcholine
and the brucine binding domains.
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molecules reversibly bindbrucine binding domainsfluorophoreligandderivativeenergy transfer binding experimentsmuscarinic M 1 receptors12 atomBodipyKinetic analysesreceptor proteinallosteric modulator brucineM 1 receptorsenergy transfer efficiency exhibitsHuman M 1 Muscarinic Receptorfluorescence resonance energy transferFluorescent Pirenzepine DerivativeslinkerEGFPdata favorPotential Bitopic Ligandspirenzepine