1
Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, 38 Nishigonaka Myodaiji, Okazaki, 444-8585, Japan.
2
COE Program for Brain Integration and its Disorders, Tokyo Medical and Dental University, Graduate School and Faculty of Medicine, Bunkyo, Tokyo, 113-8519, Japan.
3
Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012, Japan.
4
Department of Molecular Cell Signaling, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu-shi, Tokyo 183-8526, Japan.
5
Present address: Terasawa Unit, Wisconsin Regional Primate Research Center, University of Wisconsin, Madison, Wisconsin 53715, USA.
The extracellular domain of the metabotropic glutamate receptor 1 (mGluR1) forms a dimer and the ligand, glutamate, induces a structural rearrangement in this domain. However, the conformational change in the cytoplasmic domain, which is critical for mGluR1's interaction with G proteins, remains unclear. Here we investigated the ligand-induced conformational changes in the cytoplasmic domain by fluorescence resonance energy transfer (FRET) analysis of mGluR1 labeled with fluorescent protein(s) under total internal reflection field microscopy. Upon ligand binding, the intersubunit FRET efficiency between the second loops increased, whereas that between first loops decreased. In contrast, the intrasubunit FRET did not change clearly. These results show that ligand binding does not change the structure of each subunit, but does change the dimeric allocation of the cytoplasmic regions, which may underlie downstream signaling.
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