Abstract
G protein-coupled receptors (GPCRs), which constitute the largest and structurally best conserved family of signaling molecules, are involved in virtually all physiological processes. Crystal structures are available only for the detergent-solubilized light receptor rhodopsin. In addition, this receptor is the only GPCR for which the presumed higher order oligomeric state in native membranes has been demonstrated (Fotiadis, D., Liang, Y., Filipek, S., Saperstein, D. A., Engel, A., and Palczewski, K. (2003) Nature 421, 127-128). Here, we have determined by atomic force microscopy the organization of rhodopsin in native membranes obtained from wild-type mouse photoreceptors and opsin isolated from photoreceptors of Rpe65-/- mutant mice, which do not produce the chromophore 11-cis-retinal. The higher order organization of rhodopsin was present irrespective of the support on which the membranes were adsorbed for imaging. Rhodopsin and opsin form structural dimers that are organized in paracrystalline arrays. The intradimeric contact is likely to involve helices IV and V, whereas contacts mainly between helices I and II and the cytoplasmic loop connecting helices V and VI facilitate the formation of rhodopsin dimer rows. Contacts between rows are on the extracellular side and involve helix I. This is the first semi-empirical model of a higher order structure of a GPCR in native membranes, and it has profound implications for the understanding of how this receptor interacts with partner proteins.
Highlights
The atomic coordinates and structure factors have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ
The organization of rhodopsin and other G proteincoupled receptor (GPCR) in their native membranes is of paramount importance because the physiological properties of these receptors may depend on their oligomeric state
The contact sites identified in the model, which are responsible for the oligomerization of rhodopsin, are likely to be crucial for the self-assembly of other GPCRs [4, 12,13,14]
Summary
The atomic coordinates and structure factors (code 1N3M) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www.rcsb.org/). Rod outer segment (ROS) disk membranes are tightly stacked [8] The stacking of these internal cellular membrane structures ensures a dense packing of light-absorbing rhodopsins, which constitute Ͼ90% of all disk membrane proteins, and in turn, a high probability of single photon absorption [9]. The organization of rhodopsin and other GPCRs in their native membranes is of paramount importance because the physiological properties of these receptors may depend on their oligomeric state We produced a model of rhodopsin oligomers that accounts for all geometrical constraints imposed by AFM and crystallographic data. This model shows, for the first time, the higher order organization of a GPCR in its native environment. The contact sites identified in the model, which are responsible for the oligomerization of rhodopsin, are likely to be crucial for the self-assembly of other GPCRs [4, 12,13,14]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
