Molecular properties of the cGMP-gated channel of rod photoreceptors.
The cGMP-gated channel of the rod photoreceptor cell plays a key role in phototransduction by controlling the flow of Na+ and Ca2+ into the outer segment in response to light-induced changes in cGMP concentrations. The rod channel is composed of two homologous subunits designated as alpha and beta. Each subunit contains a core region of six putative membrane spanning segments, a cGMP binding domain, a voltage sensor-like motif and a pore region. In addition the beta-subunit contains an extended N-terminal region that is identical in sequence to a previously cloned retinal glutamic acid rich protein called GARP. Three spliced variants of GARP (the GARP part of the beta channel subunit; full length free GARP; and a truncated form of GARP) are expressed in rod cells and localized within the outer segments. Immunoaffinity chromatography has been used to purify the channel from detergent solubilized rod outer segments. A significant fraction of the rod Na+/Ca(2+)-K+ exchanger copurifies with the channel as measured by western blotting suggesting that the channel can interact with the exchanger under certain conditions.
Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada. molday@unixg.ubc.ca
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D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D002417:Cattle; D002846:Chromatography, Affinity; D006152:Cyclic GMP / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D008565:Membrane Proteins; D008954:Models, Biological; D011233:Precipitin Tests; D011485:Protein Binding; D017948:Retinal Rod Photoreceptor Cells / Q000737:chemistry*; D012374:Rod Cell Outer Segment; D013329:Structure-Activity Relationship
D000596:Amino Acids; D000911:Antibodies, Monoclonal; D008565:Membrane Proteins; D006152:Cyclic GMP