Effect of Polyamines on Polyphenylalanine Synthesis by Escherichia coli and Rat‐Liver Ribosomes

The addition of polyamines to an Escherichia coli cell‐free polypeptide synthetic reaction mixture containing dialyzed ribosomes, Sephadex‐treated supernatant from 1 × g centrifugation, and suitable amounts of Mg 2+ increased the polyphenylalanine synthesis from either [ 14 C]phenyl‐alanine or [ 14 C]phenylalanyl‐tRNA up to twice that synthesized in the same system without polyamines but at optimal Mg 2+ concentration. No similar effect was observed with cadaverine, agmatine, histamine, Ca 2+ or Mn 2+ . These results, together with the presence of polyamines in unwashed ribosomes and the rapid incorporation of polyamines into ribosomes incubated with polyamines, suggest that polyamines are essential components of E. coli ribosomes for maximum polypeptide synthesis. The increase of polyphenylalanine synthesis by polyamines in an E. coli cell‐free system occurred at the level of aminoacyl‐tRNA binding to ribosomes, but not at the levels of peptide bond formation and translocation. In the rat‐liver cell‐free system, an approximately 1.6‐fold increase of polyphenylalanine synthesis was observed by the addition of spermidine. However, the addition of putrescine to the reaction mixture caused only a sparing effect on the Mg 2+ requirement for polyphenylalanine synthesis.