Effects of potassium chloride concentration on protein content and polyphenylalanine synthesizing capability of 40S ribosomal subunits from canine pancreas.

Ribosomal small subunits from canine pancreas were used to survey the effects of potassium chloride in the concentration range from 0.4 to 1.25 M. When combined with 60S particles, the treated 40S subunits showed no significant change in phenylalanine incorporating activity until exposure to 0.95 M KCl. Decreases in protein content of the subunits were observed at high ionic strengths. Attempts to separate dissociated ribosomal protein and the remaining core particles treated with 1.25 M KCl by centrifugation of the salt-treated particles though a 40% sucrose cushion led to the observation that ribosomal subparticles isolated in this manner retained full phenylalanine incorporating activity, whereas centrifugation through other solutions resulted in inactive or less active particles. Experiments were performed to elucidate the mechanism by which the 40% sucrose cushion was stabilizing the high salt treated 40S subunits. Two-dimensional gel electrophoresis of the proteins of the various particles isolated in the study was performed. The active 40S particles contained 23-31 protein spots. The isolation of fully active 40S subunits with fewer proteins than previously reported should simplify elucidating their role in the function of the small subunit.