Acetylation of peptidyl-tRNA on rat liver polyribosomes

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 MKC1--5mM Mg(OAc)2 solubilized acetyltransferase activity which could catalyze histone acetylation, and the extract when added back to the extracted 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 any assay specific for the acetyl-CoA:peptidyl-tRNA N-acetyltransferase which is associated with rat liver polyribosomes.