Ribosomal Subunits from Rat Liver

Publisher Website
Google Scholar
Abstract
Ribosomal subunits from rat liver were prepared with a mild method which consisted of centrifuging ribosomes through a sucrose layer containing 0.3 M KCl. Isolated 40‐S subunits were obtained completely pure and 60‐S subunits were contaminated by less than 5% of 40‐S. In the presence of Mg2+ subunits reassociated into monosomes, which had high activity in polyphenylalanine synthesis. 40‐S, but not 60‐S, subunits could bind [3H]poly(U) and [14C]phenylalanyl‐tRNA.Both subunits could be lyophilized and then kept at room temperature without detectable change in activity nor in sedimentation profile.Determination of the chemical composition of both subunits showed that 40‐S had a higher protein content than 60‐S subunits. However concentrated‐salt washings of the 40‐S resulted in step‐wise extraction of proteins without inactivation of the subunits, whereas extraction with salt of a small amount of proteins from the 60‐S subunits completely inactivated them.Study of thermal inactivation showed that 40‐S had a significantly higher heat stability than 60‐S subunits.