Regulation of aromatic amino acid transport systems in Escherichia coli K-12.

The regulation of the aromatic amino acid transport systems was investigated. The common (general) aromatic transport system and the tyrosine-specific transport system were found to be subject to repression control, thus confirming earlier reports. In addition, tryosine- and tryptophan-specific transport were found to be enhanced by growth of cells with phenylalanine. The repression and enhancement of the transport systems was abolished in a strain carrying an amber mutation in the regulator gene tyrR. This indicates that the tyrR gene product, which was previously shown to be involved in regulation of aromatic biosynthetic enzymes, is also involved in the regulation of the aromatic amino acid transport systems.