Modulates the activity of the EnvZ/OmpR two-component regulatory system, probably by directly modulating EnvZ enzymatic activity and increasing stability of phosphorylated OmpR. Links the two-component systems CpxA/CpxR and EnvZ/OmpR. Interacts with EnvZ. Regulated by the CpxA/CpxR two-component system. Negatively regulated by EnvZ/OmpR. Interacts with EnvZ through its soluble periplasmic region. Belongs to the MzrA family.