Infection of Escherichia coli by filamentous bacteriophages is mediated by the minor phage coat protein A and involves two distinct cellular receptors, the F' pilus and the periplasmic protein TolA. These two receptors are contacted in a sequential manner, such that binding of TolA by the extreme N-terminal domain is conditional on a primary interaction of the second coat protein A domain with the F' pilus [1].

1: Crystal structure of the two N-terminal domains of g3p from filamentous phage fd at 1.9 A: evidence for conformational lability. Holliger P, Riechmann L, Williams RL; J Mol Biol 1999;288:649-657. PMID:10329170