Model of the Bpe Fluc channel with L3 monobodies bound. Ribbon representation of a model of the Bpe Fluc channel in complex with L3 monobody, constructed using the x-ray structure of Bpe Fluc in complex with L2 monobody (PDB accession no. 5FXB). Two ion permeation pathways in the antiparallel dimer are positioned lateral to the critical Phe residues (F82 and F85; yellow stick). Each L3 monobody (blue) inserts the FG loop into the pore, with E79 shown in stick representation (carbon colored yellow and oxygen red).