Booth D P, Hurwitz R L, Lolley R N
Department of Anatomy, University of California School of Medicine, Los Angeles.
J Neurochem. 1991 Jun;56(6):1949-56. doi: 10.1111/j.1471-4159.1991.tb03452.x.
Cone and rod photoreceptors utilize cyclic guanosine monophosphate (cGMP) in the light regulation of membrane polarization. The prototype for visual transduction is established for rod photoreceptors, which utilize a cascade of reactions to regulate a cyclic nucleotide phosphodiesterase (PDE) (EC 3.1.4.17) and thereby control the intracellular concentration of cGMP. Although cones appear to utilize a comparable cGMP cascade for their phototransduction, evidence exists that the PDE from cone photoreceptors may be different from that of rods. Dissociated cone photoreceptors, isolated retinas, and cone outer segments from the lizard, Anolis carolinensis, have been used to identify and characterize a PDE enzyme complex that shares several features in common with the rod outer segment (ROS) PDE complex. Immunoadsorption and sodium dodecyl sulfate-polyacrylamide gel electrophoresis have identified a subunit of lizard cone PDE that has an apparent electrophoretic mobility of 84 kDa and a subunit of lizard rod PDE that migrates at approximately 90 kDa. The lizard cone PDE complex is similar in size, extraction, activation, and immunological characteristics to the PDE complex of rod photoreceptors from lizard, bovine, and human retinas. The lizard cone PDE complex, and perhaps that from cone photoreceptors in general, differs from that of ROS in its chromatographic properties on anion-exchange resins. The sharing of physical and activation properties of the rod and cone PDE complex is compatible with the phototransduction process occurring by a similar mechanism in both cell types. The differences in light sensitivity and speed of response may be attributable to features of the individual proteins that form the PDE complexes of rods and cones or to other undisclosed features of the respective cascades.
视锥和视杆光感受器在膜极化的光调节过程中利用环鸟苷单磷酸（cGMP）。视杆光感受器建立了视觉转导的原型，其利用一系列反应来调节环核苷酸磷酸二酯酶（PDE）（EC 3.1.4.17），从而控制细胞内cGMP的浓度。尽管视锥细胞在其光转导过程中似乎利用了类似的cGMP级联反应，但有证据表明，视锥光感受器的PDE可能与视杆细胞的不同。来自绿安乐蜥的解离视锥光感受器、分离的视网膜和视锥细胞外段已被用于鉴定和表征一种PDE酶复合物，该复合物与视杆细胞外段（ROS）PDE复合物具有几个共同特征。免疫吸附和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳鉴定出绿安乐蜥视锥PDE的一个亚基，其表观电泳迁移率为84 kDa，以及绿安乐蜥视杆PDE的一个亚基，其迁移率约为90 kDa。绿安乐蜥视锥PDE复合物在大小、提取、激活和免疫学特征方面与来自绿安乐蜥、牛和人类视网膜的视杆光感受器的PDE复合物相似。绿安乐蜥视锥PDE复合物，也许一般来说视锥光感受器的PDE复合物，在阴离子交换树脂上的色谱性质与ROS的不同。视杆和视锥PDE复合物在物理和激活特性上的共享与两种细胞类型中通过类似机制发生的光转导过程相一致。光敏感性和反应速度的差异可能归因于构成视杆和视锥PDE复合物的单个蛋白质的特性，或者归因于各自级联反应的其他未公开特性。
