Studies on the interaction of Trp holorepressor with several operators. Evidence that the target need not be palindromic.

The interaction of Trp repressor protein with partial trp operators was studied in vitro and in vivo. At high ratios of protein to DNA, Trp holorepressor formed stable complexes with DNA molecules containing half operators. When plasmids conferring the capacity to hyperproduce Trp repressor were present in trpOc strains of Escherichia coli, repression of downstream tryptophan synthase occurred. Palindromicity of the trp operator may facilitate stable interaction with Trp repressor, but this attribute need not be regarded as a critically essential structural feature. Sufficient information for the recognition by Trp repressor protein of an appropriate target resides within a DNA sequence of approximately ten base-pairs.