The murPQ operon of Escherichia coli encoding the enzymes for degradation of MurNAc is derepressed by MurR (YfeT) in the presence of MurNAc-6-phosphate. MurR also represses its own expression. We found that murR is stimulated in rich medium. This activation involves MurR and most of the IIBC components of the phosphotransferase system, suggesting auto-induction of murR by an activated form of MurR.
