Acetylation of peptidyl-tRNA on rat liver polyribosomes

Abstract

Some properties of the known NH2-terminal acetylation of peptidyl-tRNA on rat liver polyribosomes were studied. Polyribosomes were incubated with [3H]acetyl-CoA and the products were separated into protein and peptidyl-tRNA fractions by an Ecteola-cellulose column procedure adapted for rapid, routine analysis of many samples, so that the characteristics of acetylation of the two fractions could be determined. Extraction of the polyribosomes with 0.5 M KCl–5 mM Mg(OAc)2 solubilized acetyltransferase activity which could catalyze histone acetylation, and the extract when added back to the extracted polyribosomes restored peptidyl-tRNA acetylation to 70% of the original values. The same extract could catalyze only a slight acetylation of peptidyl-tRNA free in solution isolated from polyribosomes by extraction with EDTA. These observations form the basis of an assay specific for the acetyl-CoA: peptidyl-tRNA N-acetyltransferase which is associated with rat liver polyribosomes.