Asymmetry of the rhodopsin dimer in complex with transducin.

Abstract

A large body of evidence for G-protein-coupled receptor (GPCR) oligomerization has accumulated over the past 2 decades. The smallest of these oligomers in vivo most likely is a dimer that buries 1000-Å(2) intramolecular surfaces and on stimulation forms a complex with heterotrimeric G protein in 2:1 stoichiometry. However, it is unclear whether each of the monomers adopts the same or a different conformation and function after activation of this dimer. With bovine rhodopsin (Rho) and its cognate bovine G-protein transducin (Gt) as a model system, we used the retinoid chromophores 11-cis-retinal and 9-cis-retinal to monitor each monomer of the dimeric GPCR within a stable complex with nucleotide-free Gt. We found that only 50% of Rho* in the Rho*-Gt complex is trapped in a Meta II conformation, while 50% evolves toward an opsin conformation and can be regenerated with 9-cis-retinal. We also found that all-trans-retinal can regenerate chromophore-depleted Rho*e complexed with Gt and FAK*TSA peptide containing Lys(296) with the attached all-trans retinoid (m/z of 934.5[MH](+)) was identified by mass spectrometry. Thus, our study shows that each of the monomers contributes unequally to the pentameric (2:1:1:1) complex of Rho dimer and Gt heterotrimer, validating the oligomeric structure of the complex and the asymmetry of the GPCR dimer, and revealing its structural/functional signature. This study provides a clear functional distinction between monomers of family A GPCRs in their oligomeric form.

DOI: 10.1096/fj.12-225383

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@article{Jastrzebska2013AsymmetryOT, title={Asymmetry of the rhodopsin dimer in complex with transducin.}, author={Beata Jastrzebska and Tivadar Orban and Marcin Golczak and Andreas Engel and Krzysztof Palczewski}, journal={FASEB journal : official publication of the Federation of American Societies for Experimental Biology}, year={2013}, volume={27 4}, pages={1572-84} }