Ionic interactions in eukaryotic ribosomes: splitting of the subunits of rat liver ribosomes by treatment with monovalent cations.

Proteins of rat liver ribosomal subunits were successively split off by stepwise treatment of the particles with various concentrations of LiC1 (0.4--1.0 M) or KC1 (0.6--1.5 M). Split proteins and core particle proteins were analyzed by two-dimensional polyacrylamide gel electrophoresis. The LiC1 concentrations were estimated at which the individual proteins are split off. The proteins of 40S and 60S subunits were classified in 4 and 5 groups, respectively, according to their splitting behavior. The effect of LiC1 and KC1 is similar, but higher concentrations of KC1 than of LiC1 are required to obtain comparable split protein patterns. Evidence for structural changes of the core particles during the split procedures was obtained.