Ramagopal S
Roche Institute of Molecular Biology, Department of Biochemistry, Nutley, NJ 07110.
Biochem Cell Biol. 1990 May;68(5):838-45.
The distribution of ribosomal proteins in monosomes, polysomes, the postribosomal cytosol, and the nucleus was determined during steady-state growth in vegetative amoebae. A partitioning of previously reported cell-specific ribosomal proteins between monosomes and polysomes was observed. L18, one of the two unique proteins in amoeba ribosomes, was distributed equally among monosomes and polysomes. However S5, the other unique protein, was abundant in monosomes but barely visible in polysomes. Of the developmentally regulated proteins, D and S6 were detectable only in polysomes and S14 was more abundant in monosomes. The cytosol revealed no ribosomal proteins. On staining of the nuclear proteins with Coomassie blue, about 18, 7 from 40S subunit and 11 from 60S subunit, were identified as ribosomal proteins. By in vivo labeling of the proteins with [35S]methionine, 24 of the 34 small subunit proteins and 33 of the 42 large subunit proteins were localized in the nucleus. For the majority of the ribosomal proteins, the apparent relative stoichiometry was similar in nuclear preribosomal particles and in cytoplasmic ribosomes. However, in preribosomal particles the relative amount of four proteins (S11, S30, L7, and L10) was two- to four-fold higher and of eight proteins (S14, S15, S20, S34, L12, L27, L34, and L42) was two-to four-fold lower than that of cytoplasmic ribosomes.
在营养型变形虫的稳态生长过程中，测定了核糖体蛋白在单体、多聚体、核糖体后胞质溶胶和细胞核中的分布。观察到先前报道的细胞特异性核糖体蛋白在单体和多聚体之间的分配情况。L18是变形虫核糖体中的两种独特蛋白之一，在单体和多聚体中分布均匀。然而，另一种独特蛋白S5在单体中含量丰富，而在多聚体中几乎不可见。在发育调控蛋白中，D和S6仅在多聚体中可检测到，而S14在单体中含量更高。胞质溶胶中未发现核糖体蛋白。用考马斯亮蓝对核蛋白进行染色后，约18种蛋白被鉴定为核糖体蛋白，其中7种来自40S亚基，11种来自60S亚基。通过用[35S]甲硫氨酸对蛋白质进行体内标记，34种小亚基蛋白中的24种和42种大亚基蛋白中的33种定位于细胞核。对于大多数核糖体蛋白来说，核前核糖体颗粒和细胞质核糖体中的表观相对化学计量相似。然而，在前核糖体颗粒中，四种蛋白（S11、S30、L7和L10）的相对含量比细胞质核糖体中的高两到四倍，而八种蛋白（S14、S15、S20、S34、L12、L27、L34和L42）的相对含量比细胞质核糖体中的低两到四倍。
