Stimulation in vitro of expression of the amp gene of pBR322 by soluble protein fractions isolated from E. coli.

Two soluble protein fractions isolated from E. coli were found to be required for efficient expression of the amp gene of pBR322 in an in vitro coupled transcription-translation system consisting of unwashed ribosomes and a polyethylene glycol-treated S30 extract from E. coli. Both fractions stimulated the pBR322-directed synthesis of the amp gene product, pre-beta-lactamase, in the in vitro system. However, pBR322-directed RNA synthesis was stimulated only by one fraction. It is therefore likely that one fraction enhances the transcription of the amp gene and the other is involved mainly in stimulation of the translation of pre-beta-lactamase mRNA.