Hollyfield J G, Rayborn M E, Verner G E, Maude M B, Anderson R E
Invest Ophthalmol Vis Sci. 1982 Apr;22(4):417-27.
The effect of light on the biosynthesis and the assembly of rod photoreceptor outer segment membranes was analyzed in vitro using retinas from Xenopus laevis. The number of open discs at the base of the outer segment was used as a morphologic index to evaluate relative differences in rates of membrane assembly. Assembly was stimulated in vitro by light, as evidenced by a greater number of open discs that accumulated in light-exposed retinas than that in retinas maintained under the same conditions but in darkness. Quantitative autoradiography indicated, however, that unlike membrane assembly, the incorporation of 3H-leucine or 3H-mannose into proteins by rods was nearly identical in light-stimulated and dark-maintained retinas. Likewise, the synthesis of opsin, a protein destined for the rod outer segment, was not affected by light. We conclude from these studies that the enhanced rate of outer segment membrane assembly that occurs during the early light phase of the diurnal cycle takes place in the absence of an increase in the rate of biosynthesis of opsin, the major outer segment membrane protein.
利用非洲爪蟾的视网膜在体外分析了光对视杆光感受器外段膜生物合成和组装的影响。外段基部开放盘的数量用作形态学指标，以评估膜组装速率的相对差异。体外实验中，光刺激了膜组装，这表现为与在相同条件下但处于黑暗中的视网膜相比，暴露于光下的视网膜积累了更多的开放盘。然而，定量放射自显影表明，与膜组装不同，视杆细胞将³H-亮氨酸或³H-甘露糖掺入蛋白质的过程在光刺激和黑暗处理的视网膜中几乎相同。同样，视蛋白（一种定位于视杆外段的蛋白质）的合成不受光的影响。我们从这些研究中得出结论，在昼夜周期的早期光照阶段，外段膜组装速率的提高是在视杆外段主要膜蛋白视蛋白的生物合成速率没有增加的情况下发生的。
