Colicin A

Colicin A is a type of Colicin, a bacteriocin made by E. Coli which acts against other nearby E. Coli to kill them by forming a pore in the membrane, leading to depolarisation of the membrane which kills the cell.

Mechanism of uptakeMechanism of uptake

Colicin A binds to the BtuB Vitamin B12 outer membrane receptor of the target cell, and uses the Tol system to translocate across the membrane, specifically TolQRAB, alongside the OmpF protein. Its use of the Tol system means that Colicin A is in the A group of colicins.

Killing ActivitiesKilling Activities

Colicin A is a pore-forming colicin, which means that its cytotoxic domain inserts into the membrane of the target cell, resulting in the depolarisation of the cell membrane. E. coli uses the polarisation of its cell membrane to generate energy, so with this not functioning a number of energy-requiring cellular functions are inhibited, and the cell ultimately dies, after an arrest of motility within 3 minutes.

Col A when present in an E. coli cell is able to affect macromolecular synthesis throughout the cell, affecting many of the processes in the cell. One such affected system is nucleic acid synthesis; it is halted very soon after Col A is added to the system. Through its affect on macromolecular synthesis it also affects certain permease activities, such as the uptake of labelled isoleucine.