Retinal counterion switch in the photoactivation of the G protein-coupled receptor rhodopsin

Yan, Elsa C. Y.; Kazmi, Manija A.; Ganim, Ziad; Hou, Jingbo; Pan, Douhai; Chang, Belinda S. W.; Sakmar, Thomas P.; Mathies, Richard A.

doi:10.1073/pnas.1531970100

Cited by 206 publications

(307 citation statements)

References 38 publications

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“…Such dimers do not exist in the single photon working range (36) of the rod photoreceptor cell. Furthermore, it remains to be studied how the sequence of catalytic steps in R*-G protein coupling identified here relate to different conformations of the activated receptor, which are separated by protonation changes in rhodopsin (2,(37)(38)(39)(40)(41). The G protein may use different receptor conformations, which can bind either CT␣ or CT␥-far, to allosterically control the affinity of the two binding sites on the receptor for efficient nucleotide exchange catalysis.…”

Section: Discussionmentioning

confidence: 99%

Sequence of Interactions in Receptor-G Protein Coupling

Herrmann¹,

Heck²,

Henklein³

et al. 2004

Journal of Biological Chemistry

110

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Guanine nucleotide exchange in heterotrimeric G proteins catalyzed by G protein-coupled receptors (GPCRs) is a key event in many physiological processes. The crystal structures of the GPCR rhodopsin and two G proteins as well as binding sites on both catalytically interacting proteins are known, but the temporal sequence of events leading to nucleotide exchange remains to be elucidated. We employed time-resolved near infrared light scattering to study the order in which the G␣ and G␥ C-terminal binding sites on the holo-G protein interact with the active state of the GPCR rhodopsin (R*) in native membranes. We investigated these key binding sites within mass-tagged peptides and G proteins and found that their binding to R* is mutually exclusive. The interaction of the holo-G protein with R* requires at least one of the lipid modifications of the G protein (i.e. myristoylation of the G␣ N terminus and/or farnesylation of the G␥ C terminus). A holo-G protein with a high affinity G␣ C terminus shows a specific change of the reaction rate in the GDP release and GTP uptake steps of catalysis. We interpret the data by a sequential fit model where (i) the initial encounter between R* and the G protein occurs with the G␤␥ subunit, and (ii) the G␣ C-terminal tail then interacts with R* to release bound GDP, thereby decreasing the affinity of R* for the G␤␥ subunit. The mechanism limits the time in which both C-terminal binding sites of the G protein interact simultaneously with R* to a short lived transitory state.In eukaryotes, signal transduction across cell membranes is in many cases based on the interplay between G protein-coupled receptors (GPCRs) 1 and heterotrimeric guanine nucleotide-binding proteins (G proteins, G␣␤␥). Binding of extracellular signaling molecules like hormones, neurotransmitters, or odorants to GPCRs triggers structural rearrangements in the receptor, such that its intracellular domain becomes competent to catalyze nucleotide exchange in the heterotrimeric G protein (1).Rhodopsin is the visual pigment in retinal rod photoreceptors, those cells responsible for seeing under dim light conditions, and is the prototypical GPCR of the large family of rhodopsin-like GPCRs. Rhodopsin's ligand, the chromophore 11-cis-retinal, is covalently bound and recognizes a photon as an extracellular signal. Within 200 femtoseconds, the energy of the photon causes cis 3 trans isomerization of the retinal, thereby triggering the conversion of inactive dark-adapted rhodopsin into the active receptor conformation (R*), which is reached after milliseconds and is capable of interacting with transducin, the G protein of the rod cell (2).High resolution structures of transducin (G t (3) and the closely related heterotrimeric G protein G i ␣ 1 ␤ 1 ␥ 2 (4)) and rhodopsin (in the dark-adapted 11-cis-retinal bound state (5)) are available ( Fig. 1). However, static crystal structures alone cannot elucidate the dynamics of the receptor-G protein interaction. Previous studies have focused on identifying structural domains involv...

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Section: Discussionmentioning

confidence: 99%

Sequence of Interactions in Receptor-G Protein Coupling

Herrmann¹,

Heck²,

Henklein³

et al. 2004

Journal of Biological Chemistry

110

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“…The only GPCR transmembrane structure available is that of rhodopsin in the inactive form (Palczewski et al, 2000), and, despite a plethora of informative biophysical studies on rhodopsin (Farrens, 1996;Dunham and Farrens, 1999;Meng and Bourne, 2001;Choi et al, 2002;Yan et al, 2003), there remains a paucity of information of the exact nature of the intramolecular changes accompanying receptor activation. In the past several years, a great deal has been learned from modeling the endodomain of LHR using ab initio and, more recently, comparative modeling approaches (Fanelli, 2000;Fanelli et al, 2001Fanelli et al, , 2004Fanelli and Puett, 2002;Fanelli and De Benedetti, 2005;Angelova et al, 2002;Ascoli et al, 2002;Zhang et al, 2005).…”

Section: Activation Of the Transmembrane Region Of Lhrmentioning

confidence: 99%

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

Puett

DeMars

et al. 2007

Molecular and Cellular Endocrinology

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The luteinizing hormone receptor (LHR) is one of eight members in a cluster of the rhodopsin family of the large G protein-coupled receptor (GPCR) superfamily that contains some 800-900 genes in the human genome. LHR, along with its paralogons, follicle stimulating hormone receptor (FSHR) and thyroid stimulating hormone receptor, form one of the three classes in this cluster; the two other classes contain the relaxin-binding GPCRs and orphan GPCRs. These GPCRs are characterized by a relatively large ectodomain (ECD) containing leucine-rich-repeats (LRRs); in the class of glycoprotein hormone receptors, the LRR region is capped by N-terminal and C-terminal cysteinerich regions. Binding of human chorionic gonadotropin (hCG) or luteinizing hormone to the LHR-ECD triggers a conformational change of the transmembrane region of the receptor facilitating binding and activation of Gs, followed by effector enzyme activation and subsequent intracellular signaling. Viewing LHR as a transmembrane anchoring protein that sequentially binds hCG and Gs to give the hCG-LHR-Gs complex, numerous interactions and conformational changes must be considered. There is, unfortunately, a paucity of structural data on LHR, but crystal structures exist for hCG, the homologous FSH-FSHR-ECD (N-terminal fragment) complex, rhodopsin (in the inactive state), an active form of Gαs (transducin), and the βγ heterodimer. Using a combined experimental (site-directed mutagenesis followed by characterization in transfected cells) and computational (homology modeling and molecular dynamics simulations) approach, good working models are being developed for the protein-protein interaction faces and, in some cases, the ensuing conformational changes induced by complex formation. hCG binding to the LHR-ECD appears to involve several LRRs; LHR activation can be described in terms of disrupting a network of H-bonds in the cytosolic halves of helices 1-3, 6, and 7; and binding of LHR to Gs involves, in large part, intracellular loop 2 binding, presumably to Gsα at its C-terminus. Major gaps exist in our understanding at the molecular level of the six-polypeptide chain complex, hCG-LHR-Gs, but considerable progress has been made in the past few years.

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“…Some experimental evidence has suggested that Glu 181 is protonated in the dark-adapted state, but transfers its proton to Glu 113 via Ser 186 and then replaces Glu 113 as the PSB counterion. 32 Other work suggests that both Glu 113 and Glu 181 are unprotonated and that both act as the PSB counterion, with Glu 181 dominating in the Meta I state. 33 We have simulated both Glu 113 and Glu 181 in their unprotonated states, and we find that structural changes occur that could lead to the PSB counterion switching from Glu 113 to Glu 181.…”

Section: Psb Counterion Switchmentioning

confidence: 99%

“…11,32,[54][55][56][57][58][59][60][61][62][63][64][65] This would involve a change in protonation states during the photocycle 33 and experimental work has confirmed that Glu 113 is the dark-state counterion and been suggestive, but not conclusive, that Glu 181 is active during the light-activated stages. 66,67 The simulation results are intriguing in suggesting that this counterion switch mechanism could be present as part of the relaxation mechanism of the protein to the retinal conformational change.…”

Section: Counterion Switchmentioning

confidence: 99%

How a small change in retinal leads to G‐protein activation: Initial events suggested by molecular dynamics calculations

Stevens

Woolf

2006

Proteins

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Rhodopsin is the prototypical G-protein coupled receptor, coupling light activation with high efficiency to signaling molecules. The dark-state X-ray structures of the protein provide a starting point for consideration of the relaxation from initial light activation to conformational changes that may lead to signaling. In this study we create an energetically unstable retinal in the light activated state and then use molecular dynamics simulations to examine the types of compensation, relaxation, and conformational changes that occur following the cis-trans light activation. The results suggest that changes occur throughout the protein, with changes in the orientation of Helices 5 and 6, a closer interaction between Ala 169 on Helix 4 and retinal, and a shift in the Schiff base counterion that also reflects changes in sidechain interactions with the retinal. Taken together, the simulation is suggestive of the types of changes that lead from local conformational change to light-activated signaling in this prototypical system.

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Retinal counterion switch in the photoactivation of the G protein-coupled receptor rhodopsin

Cited by 206 publications

References 38 publications

Sequence of Interactions in Receptor-G Protein Coupling

Sequence of Interactions in Receptor-G Protein Coupling

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

How a small change in retinal leads to G‐protein activation: Initial events suggested by molecular dynamics calculations

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