1984
DOI: 10.1021/bi00306a003
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Abstract: The occurrence of a guanine nucleotide binding protein activated by squid rhodopsin was established by examination of GTPase activity, guanine nucleotide binding, and cholera toxin catalyzed labeling of squid photoreceptor membranes. Purified squid (Loligo opalescens) photoreceptors exhibited GTPase activity that increased 3-4-fold by illumination. Half-maximal GTPase activity was observed when 2% of the rhodopsin was photoconverted to metarhodopsin. The Km of the light-regulated activity was 1 microM GTP. Bin… Show more

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Cited by 71 publications
(36 citation statements)
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“…A recent report of cholera toxincatalyzed labeling has suggested the identity of a 44-kilodalton band as squid Ga (24). One-dimensional peptide maps (19) obtained by papain digestion of bovine Ga and the 46-kilodalton band in our preparation (Fig.…”
Section: Results the Gel Lanes Inmentioning
confidence: 82%
“…A recent report of cholera toxincatalyzed labeling has suggested the identity of a 44-kilodalton band as squid Ga (24). One-dimensional peptide maps (19) obtained by papain digestion of bovine Ga and the 46-kilodalton band in our preparation (Fig.…”
Section: Results the Gel Lanes Inmentioning
confidence: 82%
“…Indeed, rhodopsin is among the most mobile of integral membrane proteins with a diffusion coefficient some 10 times greater than the integral proteins of most membranes (Poo & Cone, 1974 (Foster, 1980;Saibil & Hewat, 1987). It is intriguing, therefore, that whereas a single photobleached rhodopsin may activate up to 500 transducins in vertebrate rods (Stryer, 1986), there is far less amplification in invertebrate photoreceptors (Vandenberg & Montal, 1984); in Limulus, for example, only about eight transducins are activated per bleached rhodopsin (Kirkwood et al, 1989). There may be many explanations for this difference, but it is tempting to suggest that the immobility of invertebrate rhodopsin limits its rate of interaction with transducin and thereby limits amplification of the initial signal.…”
Section: Sensitivity Of Receptorsmentioning
confidence: 99%
“…The amino-acid sequence of rhodopsin has recently been determined in both octopus (Ovchinnikov et al, 1988) and squid (Hall et al, 1991). As in the case of vertebrate visual cells, light stimulation of rhodopsin in squid causes the activation of (at least one) G-protein (Vandenberg & Montal, 1984;Calhoon et al, 1980;Brown et al, 1991). Also, squid rhodopsin is the target of light-dependent phosphorylation (Paulsen & Hoppe, 1978).…”
Section: Introductionmentioning
confidence: 99%