Hysing J, Tolleshaug H, Curthoys N P
Department of Microbiology, Biochemistry and Molecular Biology, University of Pittsburgh.
Acta Physiol Scand. 1990 Nov;140(3):419-27. doi: 10.1111/j.1748-1716.1990.tb09017.x.
Renal uptake and degradation of cytochrome c and lysozyme were investigated, using preparations that were labelled by means of covalent coupling of either protein to iodinated tyramine-cellobiose. Following proteolytic digestion, the label remains 'trapped' within intracellular organelles. Within 15 min after intravenous injection, 43% of the [125I]tyramine-cellobiose-cytochrome c and 29% of the [131I]tyramine-cellobiose-lysozyme were recovered in the kidneys. Isopycnic sucrose-gradient fractionation indicates that the two proteins initially exhibit closely similar intracellular distributions, being associated with vesicles of an equilibrium density slightly lower than that of plasma membranes. However, within 5 min after injection, the two proteins exhibit distinctly different distribution profiles. The [125I]tyramine-cellobiose-cytochrome c is localized predominantly in the lysosomal fraction of the gradient. The [131I]tyramine-cellobiose-lysozyme is also translocated to the lysosomal fraction, but at a much lower rate. For both proteins, the rates of intracellular degradation correlate with their rates of translocation. The observed difference in their kinetics of intracellular movement suggests that the two proteins are translocated at different rates into transport vesicles.
利用通过将蛋白质与碘化酪胺 - 纤维二糖共价偶联进行标记的制剂，研究了细胞色素c和溶菌酶的肾脏摄取及降解情况。经过蛋白水解消化后，标记物仍“被困”在细胞内细胞器中。静脉注射后15分钟内，肾脏中回收了43%的[125I]酪胺 - 纤维二糖 - 细胞色素c和29%的[131I]酪胺 - 纤维二糖 - 溶菌酶。等密度蔗糖梯度分级分离表明，这两种蛋白质最初表现出非常相似的细胞内分布，与平衡密度略低于质膜的囊泡相关。然而，注射后5分钟内，这两种蛋白质表现出明显不同的分布模式。[125I]酪胺 - 纤维二糖 - 细胞色素c主要定位于梯度的溶酶体部分。[131I]酪胺 - 纤维二糖 - 溶菌酶也转移到溶酶体部分，但速率要低得多。对于这两种蛋白质，细胞内降解速率与其转移速率相关。观察到的它们在细胞内移动动力学的差异表明，这两种蛋白质以不同的速率转移到运输囊泡中。
