Characterization and Synthesis of Anacystis Ribonucleic Acids

Abstract

Photoautotroph cultures of the blue-green alga Anacystis nidulans show a pronounced maximum of 10 −7 µ g total RNA/cell in the early logarithmic growth phase and a subsequent 50% decrease during the stationary phase. The alteration of the total RNA content influences all RNA fractions in the same way. Two high-molecular weight ribosomal RNAs of 1.1 and 0.56 × 10 6 daltons, respectively, are obtained if Mg 2+ (5–10 mM) is present during the RNA extraction. Absence of Mg 2+ during the RNA extraction at 0° or heating the isolated total RNA for 1 min at 60°C in the presence of Mg 2+ results in an irreversible conversion of the 1.1 × 10 6 rRNA to 0.9 plus 0.2 × 10 6 rRNA. The 0.56 × 10 6 rRNA is found to be a very stable molecule After less than 1 min pulse-labelling of A. nidulans cells with Na 2 H 32 PO 4 and separation of the RNA fractions by MAK chromatography the radioactivity is eluted with the first part of the DNA fraction and in front of the small ribosomal RNA. Extension of the pulse-labelling to a few minutes yields radioactivity in all MAK fractions. In pulse-chase experiments the small rRNA is shown to have the most rapid turnover compared to the other RNA fractions. DNA-RNA hybridization studies demonstrate that all 3 rRNA fractions contain rapidly-labelled RNA of the non-ribosomal type, however, as competition experiments indicate, in different proportions to the amount of ribosomal precursor RNAs. Thus, the 0.9 × 10 6 fraction does not contain rapidly labelled ribosomal RNA.