[Heterogeneity of 5S ribosomal RNA of the loach Misgurnus fossilis L].

The fraction of low molecular weight RNAs from the unfertilized eggs and liver of the loach (Misgurnus fossilis) was analyzed by electrophoresis in polyacrylamide gel. The 5S rRNA from unfertilized eggs differs in its electrophoretic mobility from liver 5S rRNA in the presence of 7 M urea at 20 degree C. The electrophoretic mobilities of these two rRNAs are identical at 50 degree C. These data indicate that the loach, just as the amphibians and other teleost fishes, has two types of 5S rRNA, viz. the oocyte and somatic types. Since these molecules are of identical size, their different electrophoretic mobility should be ascribed to variations in their structure. The unfertilized eggs and liver of Misgurnus fossilis contain, apart from the major fraction, a minor fraction of 5S rRNA belonging to another type. The content of 5S rRNA in preparations of the ribosomes from unfertilized eggs is much lower comparing to tht of 5.8s rRNA than in preparations of the ribosomes from somatic tissues (muscles). A possible functional significance of different 5S rRNA types (oocyte and somatic) is discussed.