The Effects of Amino Acid Replacements of Glycine 121 on Transmembrane Helix 3 of Rhodopsin

Han, May; Lin, Steven; Smith, Steven O.; Sakmar, Thomas P.

doi:10.1074/jbc.271.50.32330

Cited by 77 publications

(117 citation statements)

References 62 publications

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“…This agrees with FTIR spectra, which show that the 9-methyl group, 13-methyl group, and ␤-ionone ring affect the early intermediates (32,50,51). In addition, for retinal binding to the opsin apoprotein, the positioning of the ␤-ionone ring and the 9-methyl group have been shown to be crucial (52,53).…”

supporting

confidence: 77%

Chromophore structural changes in rhodopsin from nanoseconds to microseconds following pigment photolysis

Jäger

Lewis

Zvyaga

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

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Rhodopsin is a prototypical G proteincoupled receptor that is activated by photoisomerization of its 11-cis-retinal chromophore. Mutant forms of rhodopsin were prepared in which the carboxylic acid counterion was moved relative to the positively charged chromophore Schiff base. Nanosecond time-resolved laser photolysis measurements of wild-type recombinant rhodopsin and two mutant pigments then were used to determine reaction schemes and spectra of their early photolysis intermediates. These results, together with linear dichroism data, yielded detailed structural information concerning chromophore movements during the first microsecond after photolysis. These chromophore structural changes provide a basis for understanding the relative movement of rhodopsin's transmembrane helices 3 and 6 required for activation of rhodopsin. Thus, early structural changes following isomerization of retinal are linked to the activation of this G protein-coupled receptor. Such rapid structural changes lie at the heart of the pharmacologically important signal transduction mechanisms in a large variety of receptors, which use extrinsic activators, but are impossible to study in receptors using diffusible agonist ligands.Rhodopsin is the light-triggered membrane receptor in rod outer segments responsible for dim-light vision. Absorption of light transforms rhodopsin (rho) into an activated state, which interacts with a heterotrimeric G protein to initiate an enzyme cascade leading to visual transduction. To reach this active state, called metarhodopsin (meta) II (1, 2), rho passes through a number of intermediates that have been characterized by UV-visible, Fourier-transform infrared (FTIR), Raman, and NMR spectroscopies, in addition to spin-labeling and biochemical studies (3-10). One way to characterize the intermediates is to trap them at low temperatures. This approach led to the classical ''bleaching'' scheme ( max values in nanometers): rho (498) 3 bathorhodopsin (batho) (542) 3 lumirhodopsin (lumi) (497) 3 meta I (480) 3 meta II (380) Scheme I However, at more physiologically relevant temperatures, time-resolved measurements up to 1 msec after photolysis reveal a new intermediate and a different kinetic scheme (3, 11). The following reaction scheme was proposed to occur during the nanosecond-to-microsecond time regime (3): rho (498) 3 batho (529) ª bsi (477) 3 lumi (492) 3 . . . Scheme II The new intermediate, blue-shifted intermediate of rho (bsi), is entropically favored and thus not trapped at low temperatures (11).The role of various structural features of the retinal chromophore in early rho photointermediates has been studied through time-resolved spectral measurements of artificial rho, in which the native chromophore is replaced by synthetically modified retinals (12). In studies of bacteriorhodopsin, timeresolved absorption spectroscopy has been shown to be particularly valuable when combined with site-directed mutagenesis to probe the roles of specific protein residues in different intermediates (13). Unti...

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supporting

confidence: 77%

Chromophore structural changes in rhodopsin from nanoseconds to microseconds following pigment photolysis

Jäger

Lewis

Zvyaga

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

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“…Previously, alanine substitution of PheVI:09 in rhodopsin demonstrated that the mutant receptor reconstituted normally with the 11-cis-retinal chromophore but that it displayed decreased ability to light-dependently activate transducin in analogy with the present observations of functional impairment in a number of other 7TM receptors (24,25). Similarly, in the cholecystokinin B receptor, alanine substitution of PheVI:09 resulted in a receptor with retained high affinity agonist binding but impaired signaling (26).…”

Section: Discussionmentioning

confidence: 65%

PheVI:09 (Phe6.44) as a Sliding Microswitch in Seven-transmembrane (7TM) G Protein-coupled Receptor Activation

Valentin-Hansen¹,

Holst

Frimurer

et al. 2012

Journal of Biological Chemistry

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Background: PheVI:09 (6.44) is highly conserved among 7TM receptors. Results: In the inactive state, PheVI:09 is locked against the backbone of TM-III but slides pass IleIII:16 (3.40) into a tight hydrophobic pocket between TM-III and TM-V during receptor activation. Conclusion:Mutational analysis and computational chemistry shows that PheVI:09 functions as a microswitch. Significance: This work clarifies the molecular mechanism of a crucial microswitch in 7TM receptor activation.

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“…Thus, structural changes in the region near Glu 122 and His 211 are required for proper repositioning of the ␤-ionone ring (27). Previous studies have show a direct interaction between 11-cis-retinal and Gly 121 in rhodopsin TM III (31)(32)(33)(34)(35). The increase in the size of Gly 121 correlated directly with the increasing dark state activity.…”

Section: Discussionmentioning

confidence: 86%

Critical Role of Transmembrane Segment Zinc Binding in the Structure and Function of Rhodopsin

Stojanović

Stitham

Hwa

2004

Journal of Biological Chemistry

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Zinc deficiency and retinitis pigmentosa are both important factors resulting in retinal dysfunction and night blindness. In this study, we address the critical biochemical and structural relevance of zinc ions in rhodopsin and examine whether zinc deficiency can lead to rhodopsin dysfunction. We report the identification of a high-affinity zinc coordination site within the transmembrane domain of rhodopsin, coordinated by the side chains of two highly conserved residues, Glu 122 in transmembrane helix III and His 211 in transmembrane helix V. We also demonstrate that this zinc coordination is critical for rhodopsin folding, 11-cis-retinal binding, and the stability of the chromophore-receptor interaction, defects of which are observed in retinitis pigmentosa. Furthermore, a cluster of retinitis pigmentosa mutations is localized within and around this zinc binding site. Based on these studies, we believe that improvement in zinc binding to rhodopsin at this site within the transmembrane domain may be a pharmacological approach for the treatment of select retinitis pigmentosa mutations. Transmembrane coordination of zinc may also be an important common principle across G-protein-coupled receptors.Several neurodegenerative disorders, Alzheimer disease, Parkinson disease, familial amyotrophic lateral sclerosis, and the transmissible spongiform encephalopathies, share a common pathogenesis involving the misfolding and aggregation of specific proteins. Mounting evidence has demonstrated the direct binding of zinc (Zn 2ϩ ) to the ␤-amyloid (Alzheimer disease), ␣-synuclein (Parkinson disease), superoxide dismutase (amyotrophic lateral sclerosis), and prion (transmissible spongiform encephalopathies) proteins, linking either the gain or loss of Zn 2ϩ binding to the progression of these severe protein misfolding disorders. Zn 2ϩ promotes aggregation of the highly fibrillogenic prion peptide, PrP106 -126 (1), and of the ␤-amyloid protein (2-4) into amyloidogenic aggregates. Clioquinol, a metal chelating agent, is currently being investigated as a potential therapeutic solution to inhibit ␤-amyloid neurotoxicity (5). In contrast, in mutant superoxide dismutase protein, loss of affinity for Zn 2ϩ results in diminished protein activity (6), reduced protein stability (7), and formation of amyloid-like filaments (8). Thus, both zinc deficiencies and excesses can lead to neurodegenerative diseases.In the G protein-coupled photoreceptor rhodopsin, there have been over 100 distinct, heritable mutations identified, many of which induce an altered protein conformation, misfolding, aggregation, and cell death, followed by the clinical manifestation of the retinal neurodegenerative disorder retinitis pigmentosa (9). Interestingly, Zn 2ϩ deficiency is also known to cause retinal neurodegeneration and night blindness (10), symptoms reminiscent of retinitis pigmentosa. Furthermore, Zn 2ϩ has been shown to directly bind rhodopsin (11,12) and to reduce rhodopsin thermal stability and regeneration with 11-cis-retinal at higher Zn 2ϩ concen...

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The Effects of Amino Acid Replacements of Glycine 121 on Transmembrane Helix 3 of Rhodopsin

Cited by 77 publications

References 62 publications

Chromophore structural changes in rhodopsin from nanoseconds to microseconds following pigment photolysis

Chromophore structural changes in rhodopsin from nanoseconds to microseconds following pigment photolysis

PheVI:09 (Phe6.44) as a Sliding Microswitch in Seven-transmembrane (7TM) G Protein-coupled Receptor Activation

Critical Role of Transmembrane Segment Zinc Binding in the Structure and Function of Rhodopsin

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