Light-dependent GTP-binding proteins in squid photoreceptors

Robinson, Phyllis R.; Wood, S F; Szuts, Ete Z.; Fein, Alan M.; Hamm, Heidi E.; Lisman, John

doi:10.1042/bj2720079

Cited by 23 publications

(28 citation statements)

References 42 publications

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“…This toxin labels two proteins with apparent molecular masses of 50 kDa and 70 kDa in eyespot preparations of C. reinhardtii (Hegemann & Harz, 1993). The detection of more than one putative Gc~-subunit in preparations of green algal eyespots is similar to observations obtained for membrane preparations of invertebrate photoreceptors (Robinson et al, 1990;Tsuda & Tsuda, 1990). In addition, cross-reactivity of antisera against conserved peptide motifs of G~-subunits with novel GTP binding proteins in the molecular mass range 66-74 kDa is known from different mammalian tissues (for references see Ma, 1994).…”

Section: Discussionsupporting

confidence: 64%

G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

Schlicher¹,

Lindén²,

Calenberg³

et al. 1995

European Journal of Phycology

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Knowledge about possible elements involved in signal transduction and adaptational phenomena during phototaxis of flagellate green algae is limited. In order to identify such putative elements we present here: (i) the isolation and characterisation of an enriched plasma membrane fraction of Spermatozopsis similis, and (ii) a comparison of the distribution of Ca2+-dependent putative kinases and G proteins, as recognised by antibodies directed against mammalian Gc~-subunits, in the plasma membrane preparation and isolated eyespot apparatuses of this green alga. In western blot analyses a 54 kDa protein reacted with an antiserum against a conserved sequence of G protein c~-subunits (anti-c~ common). A 43 kDa protein was recognised by a serum against the G~-subunit of transducin. These proteins were enriched in the eyespot fraction and to a lesser extent in the plasma membrane fraction. Two polyclonal antisera against C-terminal peptides of animal G(~-subunits also labelled a 43 kDa and 54 kDa protein in the eyespot preparations. Additionally, four putative Ca2+-dependent kinases or their catalytic subunits (47, 48, 77 and 82 kDa) were identified in the plasma membrane fraction by a gel kinase assay following electrophoretic separation. The 82 kDa protein was specifically enriched in the plasma membrane fraction, while the other putative kinases were also enriched in the eyespot fraction but not in other subcellutar fractions. Monoclonal antibodies directed against a soybean CaZ+-dependent protein kinase cross-reacted with a 6I kDa protein in the plasma membrane and a 60 kDa protein in the soluble fraction. Only a very faint response was observed in the fraction enriched in eyespot apparatuses. Our results indicate (i) a low cross-contamination of the eyespot apparatus preparation by normal plasma membrane constituents and (ii) the regulatory potential for the identified kinases and G proteins in blue/green-light-dependent photoresponses of Spermatozopsis similis.

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Section: Discussionsupporting

confidence: 64%

G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

Schlicher¹,

Lindén²,

Calenberg³

et al. 1995

European Journal of Phycology

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“…This is further supported by recent patch clamp investigations on Limulus ventral photoreceptors which have shown that there are three types of light-activated ionic channels which differ in their activation and deactivation kinetics and reversal potentials (Nagy & Stieve, 1990;Nagy, 1990). Robinson, Wood, Szuts, Fein, Hamm & Lisman (1990) recently reported that three different light-activated G-proteins exist in squid photoreceptors. Payne et al (1986a) have shown that calcium injection induces a membrane current in Limulus ventral nerve photoreceptor similar to that induced by light.…”

Section: Introductionsupporting

confidence: 55%

“…Biochemical investigations on squid photoreceptors from Tsuda & Tsuda (1990) show the existence of two light-activated G-proteins. More recently Robinson et al (1990) have shown that three light-activated G-proteins exist in the photoreceptor of the squid Loligo pealei. It is known that G-proteins are responsible for gating the light-activated channels in vertebrate photoreceptors (Fesenko, Kolesnikov & Lyubarsky, 1985;Koch & Kaupp, 1985).…”

Section: Current Components In Limulus Photoreceptormentioning

confidence: 99%

Three components in the light‐induced current of the Limulus ventral photoreceptor.

Deckert

Nagy

Helrich

et al. 1992

The Journal of Physiology

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SUMMARY1. Light-induced currents were measured in Limulus ventral nerve photoreceptors using a two-electrode voltage clamp. Three kinetically distinct components in the light-induced current could be distinguished by varying the light adaptation state of the photoreceptor and the intensity of the stimulus light.2. The components could be partly separated by choosing appropriate stimulus intensities and dark adaptation time. Thus the properties of the components could be separately studied. The first component is the first to recover after a light adaptation, appears temporally first in the light-induced response, has the lowest activation threshold and is the smallest. The second component needs a longer time to recover after an adapting illumination and its kinetics differ from that of the other components. Applying a bright stimulus to a dark-adapted cell a third component can be observed late in the response.3. The time to peak of the first and the third components depended on the stimulus intensity, but not on the dark adaptation time. The time to peak of the second component became shorter the longer the dark adaptation time. For a constant adaptation state the time to the maximum of component 2 was independent, but those of components 1 and 3 were dependent on the membrane voltage.4. To exclude the possibility of the contribution of voltage-gated currents, lightactivated currents were measured at clamp potentials more negative than -50 mV after adding 4-aminopyridine into the bath solution or injecting tetraethylammonium chloride into the cell. The properties of the three components remained unchanged under these conditions. 5. The I-V curve of the first component was flat at negative membrane potentials and had a strong outward rectification at positive membrane potentials. The I-V curve of component 3 showed a negative resistance at potentials more negative than about -30 mV. In contrast, the I-V curve for the second component was always nearly linear.6. No membrane potential was found where the light-induced current was zero.Instead, current traces close to the reversal potential showed a complex waveform indicating different reversal potentials for the three components.

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“…1 D). Both processes may operate through the same G protein, but studies in squid photoreceptors indicate that rhodopsin activates two different G proteins (Tsuda, 1987;Robinson et al, 1988), raising the possibility that each process may have its own unique G protein.…”

Section: A New Model Of Invertebrate Phototransductionmentioning

confidence: 99%

The role of the inositol phosphate cascade in visual excitation of invertebrate microvillar photoreceptors.

Frank

Fein

1991

The Journal of General Physiology

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The identity of the transmitter(s) involved in visual transduction in invertebrate microvillar photoreceptors remains unresolved. In this study, the role of inositol 1,4,5-trisphosphate (IPs) was examined in Limulus ventral photoreceptors by studying the effects on the light response of heparin and neomycin, agents that inhibit the production or action of IP 3. Both heparin and neomycin reduce responses to brief flashes of light and the transient component of responses to steps of light, and also inhibit IPa-induced calcium release, indicating that IP s plays a direct role in invertebrate visual excitation. The effects of BAPTA, a calcium buffer, were also examined and shown to be consistent with a role for IPa-mediated calcium release in visual excitation. However, all three agents fail to block the plateau component of the response to a step of light, indicating that a single pathway involving IP~ and calcium cannot solely be responsible for visual excitation in invertebrates. We suggest that the inositol phosphate cascade and a second parallel process that is not dependent on IP 3 are involved in the production of the light response.

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Light-dependent GTP-binding proteins in squid photoreceptors

Cited by 23 publications

References 42 publications

G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

Three components in the light‐induced current of the Limulus ventral photoreceptor.

The role of the inositol phosphate cascade in visual excitation of invertebrate microvillar photoreceptors.

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Light-dependent GTP-binding proteins in squid photoreceptors

Cited by 23 publications

References 42 publications

G proteins and Ca2+-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

G proteins and Ca2+-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

Three components in the light‐induced current of the Limulus ventral photoreceptor.

The role of the inositol phosphate cascade in visual excitation of invertebrate microvillar photoreceptors.

Contact Info

Product

Resources

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G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)