Some properties of viral ribonucleic acid-dependent amino acid incorporation

Abstract

The study of tobacco mosaic virus ribonucleic acid and R17 phage ribonucleic acid-dependent amino acid incorporation in the Escherichia coli system revealed the following differences: R17 ribonucleic acid-directed incorporations required higher supernatant concentrations and fewer ribosomes per ribonucleic acid molecule than those directed by tobacco mosaic virus ribonucleic acid; when S-30 preparations were used with NH 4 + instead of K +, R17 ribonucleic acid stimulation increased 10-fold while tobacco mosaic virus ribonucleic acid stimulation only increased 3-fold resulting in a reversal of the relative activities of the two messengers; finally R17 ribonucleic acid incorporations decreased more rapidly after thermal degradation than had been observed previously with tobacco mosaic virus ribonucleic acid. Competition experiments between R17 ribonucleic acid and tobacco mosaic virus ribonucleic acid, and between R17 ribonucleic acid and its thermally degraded derivatives, indicate that these messengers all use the same ribosome site. However no correlation was found between the capacity to bind to ribosomes and messenger activity. Inactivation after bond scission could not be attributed to a loss of binding capacity but rather to a loss of binding specificity.