Efficient repression by a heterodimeric repressor in Escherichia coli.

Previous studies with purified variants of the 434 repressor having different operator-binding specificities have demonstrated the interactions of a heterodimeric repressor with a hybrid operator site. The present study investigates the interactions between the 434 repressor and its operator site. The optimum 434 operator half-site is used with a P22 operator half-site to create a hybrid 434/P22 operator. We show that this hybrid operator can be efficiently bound by a heterodimeric repressor, consisting of one wild-type 434 repressor monomer and one 434 repressor monomer with the binding specificity of the P22 repressor, to bring about repression in Escherichia coli.