FIG 1 .

A model of pilus assembly in A. oris. Presented is a simplified model of pilus assembly in A. oris that is centered on the type 2 fimbriae (see the text for details); FimA, FimB, and CafA are colored green, orange, and blue, respectively. The thiol-disulfide oxidoreductase MdbA catalyzes oxidative folding of nascent protein precursors as they are translocated into the exoplasm by the Sec machinery. Reoxidation of MdbA requires the membrane-bound oxidoreductase VKOR. Folded pilin precursors are polymerized and anchored to the cell wall by the tandem sortase enzymes. It is not known how electrons generated from reoxidation of MdbA/VKOR are transferred (question mark). Dashed arrows denote potential multiple steps (adapted from data in references 22 and 23).