Expression of the Escherichia coli trpE gene in E. coli K12 bacteria: maximum level, rate and time of initiation of anthranilate synthetase production.

We have investigated the effect of alterations in the structure of the plasmid-borne Escherichia coli tryptophan (trp) coding region and other regions of the same replicon on the level, rate and time of initiation of anthranilate synthetase component I (ASase) synthesis in E. coli K12. The maximum level of ASase produced corresponds to 60%-65% of the total cellular proteins. Adding sequences downstream of the trpE coding region decreases the level but does not affect the time of initiation and rate of trpE expression (ASase synthesis). The presence of additional protein coding sequences on the plasmid outside the trpE-A region causes ASase production to start earlier and decreases the rate of ASase synthesis. A second copy of the trpE coding sequences, if present within or outside the trpE-A coding region on the same replicon, doubles the rate of synthesis of ASase and slightly increases its final level of production. The initiation of ASase production occurs earlier when the two trpE copies are located within two distinct transcription units.