Characterization of ribonucleic acid components from leaves of Phaseolus aureus.

Abstract

1 A range of minor RNA components extracted from mung bean leaves, in addition to the main cytoplasmic and chloroplast rRNA, is described. These minor components comprise cleavage produces of the Mr= 1.1 × 106 chloroplast rRNA and aggregates of cytoplasmic rRNA. 2 Five distinct fragments originate from the Mr= 1.1 × 106 chloroplast rRNA. The molecular weights of these fragments suggest that there are at least two labile sites in the larger chloroplast rRNA molecule. It is probable that cleavage of the RNA occurs in vivo in the older ribosomes. In contrast the Mr= 0.56 × 106 chloroplast rRNA is stable. 3 The cytoplasmic rRNA is stable under normal conditions of extraction and fractionation, but heating the RNA reveals hidden breaks. 4 Aggregates with Mr= 2.0, 2.5 and 2.6 × 106 were formed by heating solutions of purified cytoplasmic rRNA at 50 °C. Similar aggregates are produced by certain conditions of RNA extraction and fractionation.