FIG 7.

PE structures and PilA model. (A) Crystal structure of isolated His-tagged PE molecule. The β-strands are shown in yellow, and the α-helices are shown in red. The PE monomer comprises a β-sheet with six antiparallel β-strands and two C-terminal α-helices, with one of these being formed by the His tag. A disulfide bond between the main α-helix and the end of β4 is shown. (B) Overlay of isolated His-tagged PE (in red) and the published PE structure (20) (in green) shows a good match between the two structures. (C) Truncated PilA model (based on templates with PDB accession numbers 2HI2 and 1QVE). The β-strands are shown in yellow, and the α-helices are shown in red. PilA consists of a long N-terminal helix lying in the groove of a 4-stranded antiparallel β-sheet.