Tryptophan Promoter Derivatives on Multicopy Plasmids: A Comparative Analysis of Expression Potentials inEscherichia coli

摘要

ABSTRACTA collection of variant plasmids expressing eitherEscherichia coligalactokinase or human serum albumin under the control of severalE. coli trppromoter derivatives were constructed and studied for both efficiency of expression and regulation by tryptophan. Several variables, including the length of the upstream region, tandem duplications of a core promoter, and the insertion of thetrprepressortrpRgene onto the expression vector, were studied. It is shown that derivatives containing sequences upstream from the —35 region or multiple copies of thetrppromoter produce twofold higher levels of protein than plasmids with a minimaltrppromoter truncated at —40. We show that the expression of a heterologous protein such as albumin can be significantly improved (13vs. 7 of total proteins) if both the upstreamtrppromoter region, which enhances promoter strength, and an intacttrpRgene, are included on the plasm