THE C-TERMINAL DOMAIN OF TOIA IS THE CORECEPTOR FOR FILAMENTOUS PHAGEINFECTION OF ESCHERICHIA-COLI

Filamentous bacteriophages infecting gram-negative bacteria display tr opism for a variety of pilus structures. However, the obligatory corec eptor of phage infection, postulated from genetic studies, has remaine d elusive. Here we identify the C-terminal domain of the periplasmic p rotein TolA as the coreceptor for infection of Escherichia coil by pha ge fd and the N-terminal domain of the phage minor coat protein g3p as its cognate ligand. The neighboring g3p domain binds the primary rece ptor of phage infection, the F pilus, and blocks TolA binding in its a bsence. Contact with the pilus releases this blockage during infection . Our findings support a sequential two-way docking mechanism for phag e infection, analogous to infection pathways proposed for a range of e ukaryotic Viruses including herpes simplex, adenoviruses, and also len tiviruses like HIV-1.