Colicin E5 is a type of Colicin, a bacteriocin made by E. coli which acts against other nearby E. coli to kill them with its tRNase domain; it digests specific tRNAs, inhibiting protein synthesis and leading to the death of the cell. ColE5 is therefore an RNA restriction enzyme[1].
Synthesis and releaseSynthesis and release
The plasmid containing the gene encoding ColE5 also encodes its Colicin Immunity Protein, ImmE5. This binds to the cytotoxic domain of ColE5 and inhibits its tRNase activity while in the colicinogenic cell. The structure shows this bound to the protein.
Mechanism of uptakeMechanism of uptake
Killing ActivitiesKilling Activities
ColE5 specifically cleaves the anticodons of the tRNAs for tyr, his, asn and asp, which each share the unique sequence UQU in the loop. This activity occurs in the 115 residue C terminal domain, and the loop is cleaved between the Q (modified G) and the 3' U, which corresponds to the first and second letters of the anticodon triplet. This specificity is determined by a code YGUN surrounding the anticodon. It also cleaves the same tRNAs as above when they lack the Q[2], so the base modification unique to ColE5 sensitive tRNAs does not appear to be recognised by ColE5[3]. This structure shows the domain of ColE5.
