This protein is able to protect a cell, which harbors the plasmid ColE7 encoding colicin E7, against colicin E7, it binds specifically to the DNase-type colicin and inhibits its bactericidal activity. Dimeric ImmE7 may possess a RNase activity that cleaves its own mRNA at a specific site and thus autoregulates translational expression of the downstream ceiE7 gene as well as degradation of the upstream ceaE7 mRNA. Belongs to the colicins ColE2/ColE8/ColE9 and pyocins S1/S2 family.