Effects of aging on the various steps of protein synthesis: Fragmentation of elongation factor 2

The possible mechanism responsible for the in vivo protein synthesis declin e during aging was studied. In order to determine the effect of aging on th e various steps of protein synthesis, we determined the ribosomal state of aggregation and the time of assembly and release of polypeptide chains in t he process of protein synthesis in rat Liver. The results suggest that elon gation is the most sensitive step to aging. A molecular study of the Elonga tion Factor 2 (EF-2), the main protein involved in the elongation step, sho ws that this protein has a higher content of carbonyl groups and is less ac tive in old rats. In addition, the molecular mass analysis of EF-2 shows th at this protein becomes fragmented in old rats. A similar pattern of fragme ntation is found in 3-month-old rats suffering oxidative stress, in that th e decline in protein synthesis is similar to that found in old rats. These data suggest that: i) oxidative stress seems to be involved in the modifica tions of EF-2 observed during aging, and ii) the observed modifications (ox idation and fragmentation) of EF-2 could account for the decline in protein synthesis in old animals. (C) 1998 Elsevier Science Inc.