[In vitro degradation of autolyzed and nonautolyzed RNP-particles from rat skeletal muscles].

Degradation of autolyzed (72 hrs of autolysis) and non-autolyzed RNP particles from rat skeletal muscles was studied. Distribution of the RNP particles in sucrose gradient and the amount of rRNAs present in the particles were determined. It was shown that in both cases incubation of preparations for 20 min at 60 degrees C is accompanied by an almost complete degradation of RNA extracted from the RNP particles. After 24 hour storage in a buffer, containing Mg2+ at a concentration less than 0.006 M, partial degradation of polysomes and rRNAs occurs. Incubation in the presence of 0.5 mM p-chloromercurybenzoate results in a rapid degradation of polysomes down to monosomes, whereas no additional degradation of rRNAs occurs after 24 hrs of incubation at 18 degrees C. Autolyzed RNP particles when heated up to 50-55 degrees C for 20 min, reveal a much lower stability to p-chloromercurybenzoate than do the non-autolyzed ones. Possible existence of two forms of endoribonucleases in the RNP particles from rat skeletal muscles is discussed.