Inactivation of Ribosomes In Vitro by Colicin E₃ and Its Mechanism of Action

Abstract

The incubation of purified ribosomes with colicin E₃ results in the cleavage of a terminal fragment from the 16S ribosomal RNA. The cleavage reaction requires three components: colicin E₃, the 30S ribosomal subunit, and the 50S ribosomal subunit. An immunity factor found in extracts derived from colicinogenic cells prevents the in vitro inactivation of ribosomes by colicin E₃. Evidence is presented suggesting that it does so by binding to the colicin molecule. The mode of action of colicin E₃ in vivo can be explained by the assumption that a small fraction of the adsorbed colicin penetrates into the cell and catalytically inactivates the ribosomes.

• 30S and 50S ribosomal subunits
• immunity factor
• 16S ribosomal RNA
• colicins E1, E2, and K