Photoreception and Phototransduction in Invertebrate Photoreceptors

Tsuda, Motoyuki

doi:10.1111/j.1751-1097.1987.tb07903.x

Cited by 70 publications

(50 citation statements)

References 185 publications

(128 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In contrast to bovine rhodopsin, for octopus rhodopsin photoisomerization of the chromophore to the all-trans species leads to a stable, active form of the pigment, Acid Metarhodopsin. Like bovine rhodopsin, the inverse agonist 11-cis -retinal stabilizes octopus opsin in forming octopus rhodopsin (Tsuda et al ., 1982;Tsuda, 1987;Koutalos et al ., 1989). Because octopus Acid Metarhodopsin absorbs at considerably longer wavelengths than octopus rhodopsin, shorter wavelength light can convert most of the octopus rhodopsin to Acid Metarhodopsin while longer wavelength light can reverse this, driving all the pigment back to rhodopsin.…”

Section: Introductionmentioning

confidence: 99%

A Purified Agonist-Activated G-Protein Coupled Receptor: Truncated Octopus Acid Metarhodopsin

et al. 2004

Self Cite

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

A Purified Agonist-Activated G-Protein Coupled Receptor: Truncated Octopus Acid Metarhodopsin

et al. 2004

Self Cite

View full text Add to dashboard Cite

“…Since light depolarizes invertebrate photoreceptor cells, whereas it hyperpolarizes vertebrate rod and cone photoreceptor cells, the underlying phototransduction machinery, including that for desensitization, in invertebrate photoreceptor cells could be quite distinct from that operating in vertebrate photoreceptors (28). In an effort to explore the molecular and enzymatic properties of ORK, we purified the enzyme to apparent homogeneity for the first time as an invertebrate enzyme and cloned the cDNA encoding it.…”

mentioning

confidence: 99%

A Novel Rhodopsin Kinase in Octopus Photoreceptor Possesses a Pleckstrin Homology Domain and Is Activated by G Protein βγ-Subunits

Kikkawa

Yoshida

Nakagawa

et al. 1998

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

G protein-coupled receptor kinases (GRKs) play an important role in stimulus-dependent receptor phosphorylation and desensitization of the receptors. Mammalian rhodopsin kinase (RK) and ␤-adrenergic receptor kinase (␤ARK) are the most studied members among known GRKs. In this work, we purified RK from octopus photoreceptors for the first time from invertebrate tissues. The molecular mass of the purified enzyme was 80 kDa as estimated by SDS-polyacrylamide gel electrophoresis, and this was 17 kDa larger than that of the vertebrate enzymes. Unlike vertebrate RK, octopus RK (ORK) was directly activated by ␤␥-subunits of a photoreceptor G protein. We examined the effects of various known activators and inhibitors of GRKs on the activity of the purified ORK and found that their effects were different from those on either bovine RK or ␤ARK. To analyze the primary structure of the enzyme, we cloned the cDNA encoding ORK from an octopus retinal cDNA library. The deduced amino acid sequence of the cDNA was highly homologous to ␤ARK over the entire molecule, including a pleckstrin homology domain located in the C-terminal region, and homology to RK was significantly lower. Furthermore, Western blot analysis of various octopus tissues with an antibody against the purified ORK showed that ORK is expressed solely in the retina, which confirmed the identity of the enzyme as rhodopsin kinase. Thus, ORK appears to represent a unique subgroup in the GRK family, which is distinguished from vertebrate RK.

show abstract

“…The photoisomerization of the chromophore from 11-cis to all-trans form initiates a series of thermal transformations of the pigment, which leads to the activation of a G protein. The subsequent enzymatic cascade ultimately leads to the generation of an electrical signal in the photoreceptor cell (1,2).…”

mentioning

confidence: 99%

How vertebrate and invertebrate visual pigments differ in their mechanism of photoactivation

Nakagawa

Iwasa

Kikkawa

et al. 1999

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

Self Cite

View full text Add to dashboard Cite

In vertebrate visual pigments, a glutamic acid serves as a negative counterion to the positively charged chromophore, a protonated Schiff base of retinal. When photoisomerization leads to the Schiff base deprotonating, the anionic glutamic acid becomes protonated, forming a neutral species that activates the visual cascade. We show that in octopus rhodopsin, the glutamic acid has no anionic counterpart. Thus, the ''counterion'' is already neutral, so no protonated form of an initially anionic group needs to be created to activate. This helps to explain another observation-that the active photoproduct of octopus rhodopsin can be formed without its Schiff base deprotonating. In this sense, the mechanism of light activation of octopus rhodopsin is simpler than for vertebrates, because it eliminates one of the steps required for vertebrate rhodopsins to achieve their activating state.

show abstract

Photoreception and Phototransduction in Invertebrate Photoreceptors

Cited by 70 publications

References 185 publications

A Purified Agonist-Activated G-Protein Coupled Receptor: Truncated Octopus Acid Metarhodopsin

A Purified Agonist-Activated G-Protein Coupled Receptor: Truncated Octopus Acid Metarhodopsin

A Novel Rhodopsin Kinase in Octopus Photoreceptor Possesses a Pleckstrin Homology Domain and Is Activated by G Protein βγ-Subunits

How vertebrate and invertebrate visual pigments differ in their mechanism of photoactivation

Contact Info

Product

Resources

About