Studies on the operator-repressor-effector interactions in the glp regulon of Escherichia Coli K-12

All of the glp genes of Escherichia coli are subject to negative regulation by the glpR-encoded repressor (GlpR). Comparison of the repressor binding affinity for consensus and altered consensus operator regions showed that positions 3, 4, 5, 7 and 8 bp removed from the center of operator symmetry are most important for repressor binding. Cooperative binding of repressors to tandem operators was demonstrated. Cooperativity was maximal when two 20-base pair operators were directly repeated and decreased with the deletion of 2 base pairs or the addition of 4 base pairs between the operators. Cooperative binding was eliminated by a 6 base pair insertion between tandem operators.