[Activation of latent RNAse activity of RNP particles from rat skeletal muscles]

The dependence of activation of latent RNAse of RNP particles isolated from rat skeletal muscles, on the concentration of K+ and Mg2+ in the incubation medium and on temperature was studied. During a short-term exposure (20 min 18 degrees) of RNP particles in the buffers containing K+ at concentrations varying from 0.05 M to 0.25 M and Mg2+ at concentrations from 0.001 M to 0.01 M no effect of endogenous ribonuclease was observed. It was shown that a significant activation of latent RNAse occurs during the incubation at room temperature in 24 hours provided that the incubation medium contains Mg2+ at concentrations not higher that 0.004 M. In the presence of 0.004 M Mg2+ degradation of polysomal mRNA and partial degradation of 18 S--rRNA takes place. At Mg2+ concentration as low as 0.001 M not only mRNA but also both rRNAs are accessible to the action of activated ribonuclease. 20 min heating of RNP particles up to 55 degrees C causes insignificant degradation of the polysomes and 18 S--rRNA. The increase in temperature by 5 degrees c results in the activation of latent RNAse followed by an almost complete degradation of mRNA and rRNA. The relationship between the integrity of the ribosomal structure and activation of latent ribonuclease is discussed.