Matesic D, Liebman P A
Nature. 1987;326(6113):600-3. doi: 10.1038/326600a0.
Light-modulated cytoplasmic cGMP simultaneously controls plasma membrane Na+ conductance in visual excitation and Ca2+ entry into rods by direct interaction with the cation channel. Cytoplasmic Ca2+ in turn may set operating points and contribute to the dynamics of several enzymes that regulate cGMP levels in the dark, recovery from excitation and receptor adaptation or down regulation. Similar channels may couple electrical activity to internal nucleotide metabolism in other tissues. We here report the identification, partial purification and behaviour after reconstitution of a protein of relative molecular mass 39,000 (Mr 39K) present in both disk and plasma membranes from bovine rod outer segments that mediates these cGMP-dependent cation fluxes. Its cGMP agonist specificity, kinetic cooperativity, ionic selectivity, membrane density and other features closely match the properties of the visual cGMP-dependent conductance inferred from electrophysiological measurements.
光调制的细胞质环鸟苷酸（cGMP）通过与阳离子通道直接相互作用，在视觉兴奋过程中同时控制质膜钠电导以及钙离子进入视杆细胞。细胞质中的钙离子反过来可能设定操作点，并影响几种在黑暗中调节cGMP水平、兴奋恢复、受体适应或下调的酶的动力学。类似的通道可能将其他组织中的电活动与内部核苷酸代谢联系起来。我们在此报告了一种相对分子质量为39,000（Mr 39K）的蛋白质的鉴定、部分纯化及其重组后的行为，该蛋白质存在于牛视杆细胞外段的盘膜和质膜中，介导这些依赖cGMP的阳离子通量。其cGMP激动剂特异性、动力学协同性、离子选择性、膜密度和其他特征与从电生理测量推断出的视觉cGMP依赖性电导的特性密切匹配。
