The Ribonucleic Acids of Crithidia fasciculata*

Abstract

C. fasciculata ribosomes were 80S and dissociated into 58 and 41S subunits; on 5-50% sucrose gradients; rRNA was separated into 25, 18 and 5S compononents. The molecular sizes of the heavier rRNA species estimated by polyacrylamide gel electrophoresis were 1.24 and 0.84 M (.times. 106 daltons). The 25S RNA has a tendency to interact with the 18S RNA to give a complex is difficult to separate by sucrose gradient centrifugation. The 25S RNA is unstable and dissociates into 0.73 and 0.57 M components. The 18S RNA had molecular sizes (0.84 M) higher than the 0.7 M reported for most eukaryotes, but similar to that of Euglena and Amoeba. Ribosomal RNA hybridized 0.29% of the nuclear DNA. Mitochondrial RNA extracted by a rapid procedure was resolved into 16 and 5S components in sucrose gradients.