An initiation factor causing dissociation of E. coli ribosomes

Abstract

Purification of crude initiation factors, essential for polypeptide synthesis in cell-free systems of E. coli, yielded a fraction DF which causes dissociation of 70 S ribosomes. Its stoichiometric action on 70 S ribosomes is antagonized by increasing Mg²⁺ concentrations but not by the addition of 30 S and 50 S subunits washed with high salt concentration. GTP did not stimulate this dissociating action. 2 μg of our most purified preparation caused 100% dissociation of 100 μg of 70 S ribosomes without added GTP. DF-induced dissociation is a very rapid process at 37°C and is temperature-dependent in the range of 0°–37°C. DF, which is thermolabile factor, is much less or not effective with complexed 70 S ribosomes bearing peptidyl-tRNA and mRNA.