Colicin I receptor

Function

Colicin I receptor (Cir) is a TonB-dependent transporter of E. coli outer membrane transports Fe+3 bound to catecholates. Cir is used by colicin Ia to penetrate the cell. Upon binding to colicin Ia Cir changes its conformation enabling the colicin to insert into the inner membrane forming a voltage-dependent ion channel resulting in killing the bacteria.

Structural highlights

Cir contains an N-terminal plug domain inserted inside a 22-stranded transmembrane β barrel. The colicin Ia R domain interacts with Cir plug domain.^[1]