Fig. 3: Characterization of Vpr fibrils.

a Peptide cleavage assays of Vpr fibrils. The top panel shows the amino acid sequence of the PhrC peptide from Bacillus amyloiquefaciens. The cyan and purple lines on top and bottom of the sequence indicate the range of the 15-residue substrate and 5-residue product peptide, respectively, derived from Bacillus amyloiquefaciens PhrC. The vertical line in the PhrC sequence indicates the cleavage site of Vpr peptidase. The bottom panels show the HPLC spectra of the indicated samples. When the 15-residue substrate peptide was incubated with Vpr fibrils, a peak corresponding to synthesized 5-residue product peptide was observed on the HPLC spectra, suggesting that the cleavage occurred during incubation. The gray shades are time indicator markers. mV, millivolt. b The cryo-EM micrographs of fibrils from indicated bacteria and culture conditions. The green arrows indicate Vpr fibrils, and the blue ones indicate flagellar fibrils. c A representative negative stain micrograph of Bacillus amyloiquefaciens fibrils. We note that under negative stain EM, it is hard to distinguish flagella and Vpr fibrils. The scale bar is 100 nm. Each micrograph in panel b and c is a representative of at least three similar micrographs collected from the same sample. B. amy., Bacillus amyloiquefaciens; B. subtilis, Bacillus subtilis.