The effect of age on the initiation of protein synthesis in Drosophila melanogaster.

Polyribosome levels exhibited a marked, age-related decrease in adult Drosophila melanogaster. Since decreased polyribosome levels can be due to decreased initiation of translation, initiation was measured by determination of methionyl-tRNA binding to the 40 S and 80 S initiation complexes. Compared with 1-day-old adults, 48-day-old adults exhibited no more than a 12% decrease in methionyl-tRNA binding to 40 S subunits and a 20% decrease in binding to 80 S particles. Increased age, therefore, had relatively little effect on initiation, and the decreased polyribosomal content was probably due to the deterioration of some other component of the translation system.