Age dependent changes in the activity of the cytosolic fraction from rat liver to stimulate polysomal protein synthesis and the role of initiation factor eIF-2.

The protein synthesis stimulating activity of the cytosol from the livers of rats of different age was tested in a cell-free system using washed rat liver polysomes. This activity declines significantly with increasing age. From experiments on the effect of addition of purified eIF-2 to the cell-free polysomal/cytosolic systems as well as from changes in the Met-tRNA(f) binding activity of the cytosol it is concluded that alterations in eIF-2 play an essential role in the decrease of protein synthesis with increasing age.