Effect of colicin E3 upon the 30S ribosomal subunit of Escherichia coli

The properties of 30S ribosomal subunits from untreated and from colicin E3-treated (E3-30S) bacteria have been compared. Polyacrylamide gel electrophoresis of ribosomal proteins revealed no difference, but several studies indicated that the 16S RNA from E3-30S particles was modified. E3-16S RNA showed slightly increased resistance to heat-induced degradation and had a reduced (15 S) sedimentation coefficient on sucrose gradients. Fingerprint analyses of E3-16S RNA revealed that the 3'-terminus of the molecule had been deleted. It was concluded that a primary effect of colicin E3 is the activation of a highly specific RNase that degrades 30S ribosomal RNA in situ, and that the resulting fragment(s) are probably retained within the 30S particle.