Figure 1.

Tfp and their major pilin subunits in monoderms.

A. Tfp morphology in S. sanguinis as assessed by transmission EM after negative staining. Scale bar represents 500 nm.

B. Sequence alignment of class III signal peptides in major pilins in selected monoderm and diderm bacteria. Hydrophilic residues are shaded in orange, hydrophobic residues in blue, and neutral residues are unshaded. The site of processing by the prepilin peptidase is indicated by a vertical arrow.

C. 3D structures of major pilins in monoderm and diderm bacteria. Conserved structural features have been highlighted including the C‐terminal part of the α1 helix in red and the anti‐parallel β‐sheet in green. Nota bene: the protruding N‐terminus of the α1 helix (α1N), which corresponds to the long stretch of hydrophobic residues in the class III signal peptide and gives full‐length pilins their typical ‘lollipop’ 3D structure, is not represented here because it is often truncated in structural studies to improve protein solubility. The PDB entries that were used to generate this figure are: 5JW8 (N. meningitidis), 1OQV (V. cholerae), 6I2O (S. sanguinis) and 4PE2 (C. difficile).