Cassia R O, Pucciarelli M G, Conde R D
Instituto de Investigaciones Biologicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Argentina.
Horm Metab Res. 1991 Dec;23(12):585-9. doi: 10.1055/s-2007-1003761.
The effect of protein depletion and refeeding on the metabolism of mouse liver nuclear proteins was studied. Five days protein depletion caused a 35% decrease in total nuclear protein. A fast recovery of the lost proteins, except histones, was induced when depleted mice were refed with a normal diet. Depletion caused a decrease in total nuclear protein synthesis, whereas refeeding quickly restored its normal value. The rates of total nuclear protein breakdown were estimated either as the difference between synthesis and protein gain or from the decay of radioactivity in protein labeled by the administration of both sodium [14C]bicarbonate and [35S]methionine. By these procedures, it was found that refeeding caused a slowdown in total nuclear protein breakdown. Hence, the recovery of the protein content observed during refeeding is due to both a restoration of synthesis and a decrease of breakdown. The [14C]bicarbonate procedure did not permit to obtain a high efficiency of label and, therefore, it was unsatisfactory for the measurement of the breakdown of fractionated nuclear proteins. A labeling procedure using [35S]methionine was designed for adequate measures of the decay of radioactivity in these proteins. This allows us to find that a slow down in breakdown affects similarly during refeeding to histones, to non histones, and to a fraction which contains ribonucleoproteins and soluble proteins.
研究了蛋白质缺乏和再喂养对小鼠肝脏核蛋白代谢的影响。五天的蛋白质缺乏导致核蛋白总量下降35%。当给缺乏蛋白质的小鼠重新喂食正常饮食时，除组蛋白外，丢失的蛋白质迅速恢复。蛋白质缺乏导致核蛋白合成总量下降，而再喂养则迅速使其恢复到正常值。核蛋白总分解率可通过合成与蛋白质增加量之间的差值来估算，也可根据给予[14C]碳酸氢钠和[35S]甲硫氨酸标记的蛋白质中放射性的衰减来估算。通过这些方法发现，再喂养导致核蛋白总分解减缓。因此，再喂养期间观察到的蛋白质含量恢复是由于合成的恢复和分解的减少。[14C]碳酸氢钠法无法获得高效率的标记，因此，用于测量分级核蛋白的分解并不理想。设计了一种使用[35S]甲硫氨酸的标记程序，用于充分测量这些蛋白质中放射性的衰减。这使我们发现，再喂养期间分解减缓对组蛋白、非组蛋白以及包含核糖核蛋白和可溶性蛋白的部分产生类似影响。
