[Knockout of tyrR gene in Escherichia coli and its effects on the phenylalanine biosynthesis].

Abstract

TyrR is a global regulation protein encoded by tyrR gene which controls several transcriptional units involving biosynthesis and transportation of aromatic amino acids in Escherichia coli. In this work, the tyrR gene was knocked out by a double-cross homologous recombination. The tyrR- mutant was verified by structural identification by PCR and sequencing, and functional demonstration using lacZ reporter gene. In tyrR- mutant, the activities of two key enzymes in the phenylalanine biosynthesis pathway, whose expression was controlled by TyrR, DAHPS and AT, had been shown to elevate by a 1.08-fold and 2.70-fold compared with the parent strain, respectively. The yield of phenylalanine biosynthesis in the mutant was 1.59 times higher than that of wild type strain. The repression on the transcription of aroP, encoding an aromatic amino acid permease, was eliminated, resulting in a 70.2% increase of the aromatic amino acid transportation in tyrR- mutant strain.