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.
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Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada. molday@unixg.ubc.ca
Molday
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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