Regulation of initiation and elongation factor levels in Escherichia coli as assessed by a quantitative immunoassay.

These studies are directed toward determining whether the structural genes for protein biosynthetic factors comprise an operon subject to coordinate regulation in Escherichia coli. To assess coordinate expression of these genes, an immunoassay was devided to enable accurate quantitation of initiation and elongation factors in crude bacterial extracts. The antibodies made against highly purified initiation factor 2 (IF-2A and IF-2B) and elongation factor G (EF-G) are shown to inhibit the appropriate in vitro reactions and precipitate proteins co-migrating with appropriate factors on polyacrylamide gels. Immunoprecipitation in combination with gel electrophoresis was employed to make quantitative measurements of the amounts of IF-2 (A and B) relative to EF-G present in cells at different growth rates. The results show that the ratio of EF-G to IF-2 varies in a consistent way with the generation time of the cell. IF-2 levels remain constant as cells double more rapidly, WHEREAS THE EF-G content increases with more rapid cell growth.