Three-dimensional structure of an invertebrate rhodopsin and basis for ordered alignment in the photoreceptor membrane 1 1Edited by D. Rees

Davies, Anthony; Gowen, Brent; Krebs, Angelika; Schertler, Gebhard F. X.; Saibil, Helen R.

doi:10.1006/jmbi.2001.5167

Cited by 69 publications

(65 citation statements)

References 60 publications

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“…However, the arrangements of the seven helices were found to be different on the basis of earlier low-resolution studies on rhodopsin using cryo-electron microscopy at 7.5 Å resolution in the plane of the membrane and at 16.5 Å resolution perpendicular to the membrane (130)(131)(132) [see structural comparison in (28)]. The projection map of invertebrate rhodopsin is also similar to maps previously determined for bovine and frog rhodopsins (133). In rhodopsin, the helices are slightly longer than those of bacteriorhodopsin and differently arranged.…”

Section: Previous Models: Prediction Bacteriorhodopsin and Cryo-elecsupporting

confidence: 55%

G Protein-Coupled Receptor Rhodopsin: A Prospectus

Filipek

Stenkamp

Teller

et al. 2003

Annu. Rev. Physiol.

228

196

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Rhodopsin is a retinal photoreceptor protein of bipartite structure consisting of the transmembrane protein opsin and a light-sensitive chromophore 11-cis-retinal, linked to opsin via a protonated Schiff base. Studies on rhodopsin have unveiled many structural and functional features that are common to a large and pharmacologically important group of proteins from the G protein-coupled receptor (GPCR) superfamily, of which rhodopsin is the best-studied member. In this work, we focus on structural features of rhodopsin as revealed by many biochemical and structural investigations. In particular, the high-resolution structure of bovine rhodopsin provides a template for understanding how GPCRs work. We describe the sensitivity and complexity of rhodopsin that lead to its important role in vision.

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Section: Previous Models: Prediction Bacteriorhodopsin and Cryo-elecsupporting

confidence: 55%

G Protein-Coupled Receptor Rhodopsin: A Prospectus

Filipek

Stenkamp

Teller

et al. 2003

Annu. Rev. Physiol.

228

196

View full text Add to dashboard Cite

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“…Moreover, a single cysteine substitution on the extracellular side of TM 4 abolished the cross-linking. The authors conclude that dopamine D2 receptors reside in the membrane as symmetric dimers, oriented about a TM 4 interface, in an arrangement similar to that observed by electron microscopy studies of crystals of squid rhodopsin (19). It will be of great interest to determine if other GPCRs utilize similar dimer interfaces and, if so, what role dimerization plays in receptor function.…”

supporting

confidence: 51%

“…Therefore, to obtain information about the helical packing between adjacent molecules we relied on projection maps generated by cryoelectron microscopy. Electron density projection maps have been obtained for bovine (46,47), frog (48), and squid (19) rhodopsin. Comparisons of the helical orientation and packing of the vertebrate and invertebrate rhodopsins show some interesting differences.…”

Section: Introduction Of Cysteines In the Intracellular Loops And Coomentioning

confidence: 99%

C5a Receptor Oligomerization

Klco

Lassere

Baranski

2003

Journal of Biological Chemistry

108

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G protein-coupled receptors (GPCRs), stimulated by hormones and sensory stimuli, act as molecular switches to relay activation to heterotrimeric G proteins. Recent studies suggest that GPCRs form dimeric or oligomeric structures, a phenomenon that has long been established for growth factor receptors. The elucidation of the domains of GPCRs that mediate receptor association is of critical importance for understanding the function of GPCR oligomers. Using a disulfide-trapping strategy to probe the intermolecular contact surfaces, we demonstrate cross-linking of C5a receptors in membranes prepared from both human neutrophils and stably transfected mammalian cells that is mediated by a cysteine in the second intracellular loop. To explore other surfaces that might be involved in the oligomerization of C5a receptors, we constructed receptors with individual cysteines in other intracellular regions. C5a receptors with a cysteine in the first intracellular loop or the carboxyl terminus displayed the fastest kinetics of dimer formation, whereas an intracellular loop 3 cysteine displayed minimal cross-linking. Since the rate of disulfide trapping reflects the proximity of sulfhydryl groups, assuming similar accessibility and flexibility, these results imply a symmetric dimer interface that may involve either transmembrane helices 1 and 2 or helix 4. However, neither model can account for the ability of the native cysteine in the second intracellular loop to mediate efficient crosslinking. Based on these observations, we propose that C5a receptors form higher order oligomers (i.e. tetramers) or clusters in the membrane.G protein-coupled receptors (GPCRs) 1 are an evolutionarily conserved family of transmembrane receptors that are characterized by seven-transmembrane helixes connected by intracellular loops (ICs) and extracellular loops (1, 2). GPCRs mediate a multitude of physiologic responses and serve as common pharmacological targets; more than half of all pharmacological agents that are currently prescribed target GPCRs (3). Receptor activation is accomplished by a remarkably diverse group of ligands to catalyze the exchange of GTP for GDP on the ␣ subunit of heterotrimeric G proteins. This exchange results in the dissociation of the ␣-GTP subunit from the ␤␥ dimer. Both complexes can then activate downstream targets, such as effector enzymes and ion channels (4, 5).Despite numerous structure-function studies of many different GPCRs, a fundamental question remains: Do GPCRs function as monomers or as oligomers? For the ϳ25 members of class C receptors, the answer is clear. These receptors form dimers through specialized structures, such as disulfidebonded extracellular domains (metabotropic glutamate receptors) (6, 7) or coiled-coil interactions of the carboxyl-terminal tails (GABA B receptors) (8). For the more than 500 members of the rhodopsin family of GPCRs and the 60 members of the secretin family of GPCRs, studies now demonstrate that a rapidly increasing number of these GPCRs form oligomers (9, 10). Early work...

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“…Because of the helix tilt, they diverge, and at the opposite side of the membrane they are about 35 Å apart. This 1/1 contact is conserved in all two-dimensional crystal forms of bovine and frog rhodopsin (33,34,50) but differs from the dimer observed in the squid rhodopsin crystal (54). Although rhodopsin often crystallizes as a dimer, it is not clear whether the dimer has physiological relevance.…”

Section: Discussionmentioning

confidence: 91%

The Three-dimensional Structure of Bovine Rhodopsin Determined by Electron Cryomicroscopy

Krebs

Edwards

Villa

et al. 2003

Journal of Biological Chemistry

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G-protein-coupled receptors are integral membrane proteins that respond to environmental signals and initiate signal transduction pathways, which activate cellular processes. Rhodopsin, a well known member of the G-protein-coupled receptor family, is located in the disk membranes of the rod outer segment, where it is responsible for the visualization of dim light. Rhodopsin is the most extensively studied G-protein-coupled receptor, and knowledge about its structure serves as a template for other related receptors. We have gained detailed structural knowledge from the crystal structure (1), which was solved by x-ray crystallography in 2000 using three-dimensional crystals. Here we report a three-dimensional density map of bovine rhodopsin determined by electron cryomicroscopy of two-dimensional crystals with p22 1 2 1 symmetry. The usage of relatively small and disordered crystals made the process of structure determination challenging. Special attention was paid to the extraction of amplitudes and phases, since usable raw data were limited to a maximum tilt of 45°. In the refinement process, an improved unbending procedure was applied. This led to a final resolution of 5.5 Å in the membrane plane and ϳ13 Å perpendicular to it, making our electron density map the most accurate map of a G-protein-coupled receptor currently available by electron microscopy. Most important is the information we gain about the center of the membrane plane and the orientation of the molecule relative to the bilayer. This information cannot be retrieved from the three-dimensional crystals. In our electron density map, all seven transmembrane helices were identified, and their arrangement is in agreement with the arrangement known from the crystal structure (1). In the retinal binding pocket, a density peak adjacent to helix 3 suggests the position of the ␤-ionine ring of the chromophore, and in its vicinity several of the bigger amino acids can be identified. G-protein-coupled receptors (GPCRs)1 are a large group of integral membrane proteins that provide molecular links between extracellular signals and intracellular processes (2-7). Many neurotransmitters, hormones, and drugs produce their intracellular signaling through the mediation of G-protein-coupled receptors. The binding of a hormone or neurotransmitter causes a change in the structure of the receptor, which then activates a G-protein. Different members of the receptor family respond to different ligands, and the binding site for these ligands is in the membrane-embedded part of the protein (8, 9).One of the most widely studied GPCRs is rhodopsin (1, 10 -18). Rhodopsin, located in the retina disc membrane of the eye, is responsible for the visualization of dim light. It is composed of the protein opsin (ϳ40 kDa) covalently linked to 11-cis-retinal through Lys 296 of helix 7 (19). The chromophore 11-cis-retinal isomerizes upon light activation to its all-trans conformation, which changes the arrangement of the transmembrane helices (20). This triggers the signal transduction c...

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Three-dimensional structure of an invertebrate rhodopsin and basis for ordered alignment in the photoreceptor membrane 1 1Edited by D. Rees

Cited by 69 publications

References 60 publications

G Protein-Coupled Receptor Rhodopsin: A Prospectus

G Protein-Coupled Receptor Rhodopsin: A Prospectus

C5a Receptor Oligomerization

The Three-dimensional Structure of Bovine Rhodopsin Determined by Electron Cryomicroscopy

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