FIGURE 3.
CsgB and CsgB(Δ1–8) form SDS/urea-resistant fibrils. A, the primary sequence of CsgB as coded by plasmid pFPS186. A similar plasmid was constructed but with a disruption to the secretory sequence (pFPS184[CsgB(Δ1–8)]). Tyrosine residues (underlined) of CsgB were labeled with 13C at the carbonyl position for the PITHIRDS-CT experiments. B, fibrils were examined by SDS-PAGE: CsgB fibrils suspended in 8 m urea and 2% SDS without (lane 1) and with (lane 2) 88% formic acid pretreatment are shown; similarly CsgB(Δ1–8) is shown without (lane 3) and with (lane 4) pretreatment. C, electron micrograph (28,000× direct magnification) of CsgB fibers after 1 day in Tris-saline buffer. D, CsgB(Δ1–8) fibers after 1 day.