Acidic Ribosomal Proteins from Eukaryotic Cells

Abstract

Precipitation of Saccharomyces cerevisiae ribosomes by ethanol under experimental conditions that do not release the ribosomal proteins can affect the activity of the particles. In the presence of 0.4 M NH4Cl and 50% ethanol, only the most acidic proteins from yeast and rat liver ribosomes are released. At 1 M NH4Cl two more non-acidic proteins are lost from the ribosomes. The release of the acidic proteins causes a small inactivation of the polymerizing activity of the particles, in addition to that caused by the precipitation itself. The elongation-factor-2-dependent GTP hydrolysis of the ribosomes is more affected by the loss of acidic proteins. These proteins can stimulate the GTPase, but not the polymerizing activity when added back to the treated particles. Eukaryotic proteins cannot be substituted for bacterial acidic proteins L7 and L12. Immunological cross-reaction was not detected between acidic proteins from Escherichia coli and those from yeast, Artemia salina and rat liver or between acidic proteins from these eukaryotic ribosomes among themselves.