Polyamines, equilibrium between ribosomal particles and protein synthesis in bacteria

When putrescine is added to polyamine starved cultures of an E. coli strain difficient in the biosynthesis of putrescine, the protein synthesis is enhanced almost immediately and the ribosomal pattern changes concomitantly, increasing the ratio 70S monomer/ribosomal subparticles. Studies with cell-free systems derived from polyamine starved or unstarved bacteria show that the translation of synthetic and natural mRNAs is several fold higher in system prepared from cells grown in the presence of polyamines. This effect depends on the ribosomal particles and more specifically on the 30S subunit. The results on association of ribosomal subunits strongly suggest that polyamines are involved in this reaction occurring in vivo.