Zavortink M, Thacher T, Rechsteiner M
J Cell Physiol. 1979 Jul;100(1):175-85. doi: 10.1002/jcp.1041000118.
Iodinated proteins were degraded after injection into HeLa cells at first-order rates with half-lives varying from three hours for the trout monhistone chromosomal protein, HMG-T, -to 60 hours for whale myoglobin. Fluoresceinated-bovine serum albumin (fl-BSA) was degraded almost twice as fast as unmodified BSA. The rate of degradation of 125I-BSA was very similar in eight cell lines of mouse, human, monkey and rat origin. Microinjected proteins were analyzed on SDS-acrylamide gels after injection, and for BSA and immunoglobin G, all remaining intracellular 125I migrated at the molecular weight of the injected proteins. By contrasting, more than 80% of the extracellular 125I chromatographed as iodotyrosine. With the exception of fl-BSA, which exhibited perinuclear accumulation in approximately one-half of the injected cells, autoradiography showed that throughout the period of study the injected proteins remained dispersed in the cytoplasm.
碘化蛋白质注入HeLa细胞后以一级速率降解，半衰期从鳟鱼单核小体染色体蛋白HMG-T的3小时到鲸肌红蛋白的60小时不等。荧光素标记的牛血清白蛋白（fl-BSA）的降解速度几乎是未修饰BSA的两倍。125I-BSA在源自小鼠、人类、猴子和大鼠的8种细胞系中的降解速率非常相似。注射后在SDS-聚丙烯酰胺凝胶上分析显微注射的蛋白质，对于BSA和免疫球蛋白G，所有剩余的细胞内125I都以注射蛋白质的分子量迁移。相比之下，超过80%的细胞外125I以碘酪氨酸的形式层析。除了fl-BSA在大约一半的注射细胞中表现出核周积累外，放射自显影显示在整个研究期间，注射的蛋白质仍分散在细胞质中。
