Imms bind specifically to cognate colicins in order to protect their host cells. Imm-E5 is a specific inhibitor protein of colicin E5. It binds to E5 C-terminal ribonuclease domain (CRD) to prevent cell death. The binding mode of E5-CRD and Imm-E5 mimics that of mRNA and tRNA suggesting an evolutionary pathway from the RNA-RNA interaction through the RNA-protein interaction of tRNA/E5-CRD.
Jiyao W et al.(2023). "The conserved domain database in 2023.",