Turnover of protein synthetic elongation and initiation factors in Escherichia coli.

In an effort to understand the regulation of expression of the factors required for protein biosynthesis, we have measured the turnover of elongation factor G (EF-G) and initiation factor 2 (IF-2). Using a quantitative assay which involves immunoprecipitation and gel electrophoresis, it was found that both of these factors are very stable cellular proteins, but that their rates of accumulation are quite different, indicating a differential rate of synthesis. The effects of amino acid starvation and the relaxed response were also examined. The results showed that under these conditions EF-G and IF-2 are neither synthesized nor degraded.