Specific inhibition of the termination process of protein synthesis by negamycin

The effect of negamycin and its derivatives on protein synthesis in an Escherichia coli cell-free system was determined. (1) Unlike tetracycline and streptomycin, negamycin did not inhibit codon-specific binding of aminoacyl-tRNA to ribosomes. (2) The miscoding activity of the genamycin family compounds was not parallel with the activity inhibiting the termination reaction. (3) Although negamycin strongly inhibited the overall termination reaction, it inhibited only slightly the two substeps involved; the formation of releasing factor 1 - U-A-[3H]G - ribosome complex and the peptidyl-transferase action (release of formylmethionine from the initiation complex by puromycin). (4) The termination reaction performed with ribosomes from either streptomycin- or kanamycin-resistant E. coli cells was sensitive to negamycin. These results indicate that the inhbitory effect of negamycin on the termination reaction is specific to negamycin and distinct from that of tetracycline and streptomycin.