Watson A L, László L, Doherty F J
Department of Biochemistry, University Medical School, Queen's Medical Centre, Nottingham, U.K.
Acta Biol Hung. 1991;42(1-3):49-56.
Covalent ligation of multiple copies of ubiquitin to proteins is known to target intracellular proteins for degradation by large molecular weight cytosolic proteinase(s). Ubiquitin protein conjugates are found in cytosolic cell compartments suggesting that ubiquitination may have multiple roles. We have detected ubiquitinated proteins in the lysosomal apparatus of normal fibroblasts and fibroblasts treated with lysosomal proteinase inhibitors. In contrast rabbit reticulocytes lack lysosomes. We present here direct evidence for ubiquitination of mitochondrial proteins during rabbit reticulocyte maturation. In addition ubiquitination appears to be associated with the terminal differentiation of human keratinocytes. These results suggest that: 1. ubiquitin-protein conjugates may be degraded lysosomally 2. organellar proteins may be degraded by the ubiquitin system 3. ubiquitination is involved in the programmed elimination of proteins and organelles from several cell types during differentiation.
已知将多个泛素分子共价连接到蛋白质上可将细胞内蛋白质靶向，以便被大分子质量的胞质蛋白酶降解。泛素蛋白缀合物存在于细胞质细胞区室中，这表明泛素化可能具有多种作用。我们在正常成纤维细胞和用溶酶体蛋白酶抑制剂处理的成纤维细胞的溶酶体装置中检测到了泛素化蛋白。相比之下，兔网织红细胞缺乏溶酶体。我们在此提供兔网织红细胞成熟过程中线粒体蛋白泛素化的直接证据。此外，泛素化似乎与人角质形成细胞的终末分化有关。这些结果表明：1. 泛素 - 蛋白缀合物可能被溶酶体降解；2. 细胞器蛋白可能被泛素系统降解；3. 泛素化参与了几种细胞类型在分化过程中蛋白质和细胞器的程序性清除。
