Aton B, Litman B J
Exp Eye Res. 1984 Jun;38(6):547-59. doi: 10.1016/0014-4835(84)90173-8.
Soluble enzymes, extracted from bovine retinal rod outer segments (ROS), were recombined with native ROS discs and discs which had been modified either by protease treatment or phosphorylation with rhodopsin kinase. The effect of these modifications on rhodopsin's ability to light-activate the ROS phosphodiesterase was determined. Trypsin, short-term thermolysin, and papain-digested discs were more effective in activating the phosphodiesterase than were undigested discs, whereas phosphorylated discs showed reduced ability to activate the phosphodiesterase. When a non-hydrolyzable analogue was employed in place of GTP in the assay, the same differences in the activation of phosphodiesterase as described above were observed between control discs and discs which were digested with thermolysin or phosphorylated. The proteolysis treatments remove various segments of amino acids from the carboxyl terminus of rhodopsin. In addition, at least seven phosphorylation sites are located in the terminal 15 amino acid residues of the carboxyl terminus of rhodopsin. Hence, it would appear from these studies that modifications of rhodopsin which affect the carboxyl terminus result in marked changes in the level of light-activatable phosphodiesterase activity, strongly suggesting a regulatory involvement in the light-activation process for this portion of rhodopsin.
从牛视网膜视杆外段（ROS）中提取的可溶性酶，与天然ROS盘以及经蛋白酶处理或用视紫红质激酶磷酸化修饰的盘重新组合。确定了这些修饰对视紫红质光激活ROS磷酸二酯酶能力的影响。胰蛋白酶、短期嗜热菌蛋白酶和木瓜蛋白酶消化的盘比未消化的盘在激活磷酸二酯酶方面更有效，而磷酸化的盘激活磷酸二酯酶的能力降低。当在测定中使用不可水解的类似物代替GTP时，在对照盘与用嗜热菌蛋白酶消化或磷酸化的盘之间观察到与上述相同的磷酸二酯酶激活差异。蛋白水解处理从视紫红质的羧基末端去除了各种氨基酸片段。此外，至少七个磷酸化位点位于视紫红质羧基末端的最后15个氨基酸残基中。因此，从这些研究看来，对视紫红质羧基末端的修饰导致光激活磷酸二酯酶活性水平的显著变化，强烈表明该部分视紫红质在光激活过程中具有调节作用。
