Effects of Various Triamines on Cell-Free Polypeptide Synthesis of Escherichia coli and on Growth of Its Polyamine Auxotrophs

The effects of various synthetic triamines having a general structure, H₂N(CH₂)_XNH(CH2)_>,NH2, where jt = 2—5 andy; = 2—8 (abbreviated, x-y; with 3–4 being spermidine itself), on po!y(U)-directed polypeptide synthesis of Escherichia coli and on growth of its polyamine-requiring mutants were examined in comparison with those of spermidine. Except for 2–2 and 2–3, all of the triamines stimulated more or less polypeptide synthesis at suboptimal Mg²⁺ concentrations, but the Mg²⁺ concentration required for the maximal stimulatory effect was different for each triamine. The degree of maximal stimulation caused by 3–3 (norspermidine), 4–4 (homospermidine), or 4–5 was nearly comparable with that by spermidine. The acetylspermidines were inactive, however, they inhibited the spermidine-stimulated polyphenylalanine synthesis. Many of the triamines examined reduced the ratio of leucine to phenylalanine incorporation into polypeptides during poly(U)-directed translation, and the degree of this effect did not necessarily correspond with that of the stimulatory effect. Moreover, 2–4, 2–5, 3–3 and 4–4 could stimulate the growth of a polyamine auxotroph of E. coli, MA 261, as effectively as did spermidine. However, 3–3 was the only triamine which could fully replaced spermidine in promoting growth of a mutant strain, KK 101, which is more dependent on polyamines than MA 261. Thus, these results demonstrated that some synthetic triamines were as active as spermidine in eliciting these effects, and also that there were some differences among these effects in the structural requirement for triamine.