Regulation of cyclic GMP binding to retinal rod membranes by calcium.
The apparently cooperative binding of 8-(5-thioacetamidofluorescein)-cGMP (SAF-cGMP) to cGMP-binding sites of the rod outer segments is regulated by Ca2+ in the 0.1-1 microM activity range. High Ca2+ reduces, and low Ca2+ increases the affinity of SAF-cGMP binding. This regulation involves only intrinsic membrane components. It is proposed that an allosteric regulation of cGMP binding by Ca2+ can contribute to photoreceptor potential adaptation.
Caretta
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Istituto di Fisiologia Umana, Università di Parma, Italy.
Cavaggioni
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Grimaldi
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Sorbi
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RT
D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D002463:Cell Membrane Permeability; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism*; D005452:Fluoresceins / Q000378:metabolism; D010786:Photoreceptor Cells / Q000378:metabolism* / Q000502:physiology; D012374:Rod Cell Outer Segment / Q000378:metabolism*
D005452:Fluoresceins; C049144:8-(5-thioacetamidofluorescein)cyclic-GMP; D006152:Cyclic GMP; D002118:Calcium