Effects of age on the post-initiation stages of protein synthesis.

The peptide chain elongation stage of protein synthesis in Drosophila melanogaster was found to decrease markedly with age. The decrease paralleled the age-related decrease in overall protein synthesis. In contrast, the termination stage showed little decrease until the organisms were very old. Of the three reactions that comprise peptide chain elongation, the binding of aminoacyl-tRNA to ribosomes decreased greatly with age, and the decrease paralleled that of peptide chain elongation and of overall protein synthesis. The peptidyl transfer reaction decreased moderately, and the translocation reaction exhibited no measurable decrease with age. Thus, decreased binding of aminoacyl-tRNA to ribosomes appeared to be a major contributor to the age-related decreases in peptide chain elongation and overall protein synthesis.