Open AccessStudies on a Factor Enhancing Colicin E3 Activity In Vitro
Author(s) -
Yoshinori Ohsumi,
Kazutomo Imahori
Publication year - 1974
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.71.10.4062
Subject(s) - ribosome , colicin , escherichia coli , in vitro , biochemistry , ribosomal rna , biology , chemistry , rna , gene
The mechanism of action of colicin E3 (E3) was investigated in anin vitro system. Purified ribosomes are less susceptible to E3 than crude or washed ribosomes. A factor was found in the supernatant fraction of normalEscherichia coli cells that stimulates inactivation of ribosomes by E3, and on addition of this factor, about one tenth as much E3 was required for inactivation of ribosomes. On heating a mixture of E3 and this factor above 60°, the ribosome inactivating activity of E3 increased greatly, and an amount corresponding to 0.01 μg of E3 was sufficient to inactivate 1.0A 260 unit of ribosomes completely. By this treatment bacteriocidal activity of E3 decreased considerably, as the ratio of the two activities of E3 (ribosome inactivating activity and bacteriocidal activity) increased to 6 × 104 -fold. It is evident that the two activities do not run in parallel.This heat-treated product cleaved 16S rRNA in the same way as E3. These results suggest that inactivation of ribosomes is not due to colicin molecules prepared by the standard procedure, but to a modified form of them.