Fig. 1.

Bioinformatic analysis of PilB. (A) Relevant features of PilB from S. sanguinis 2908. The N-terminal class III signal peptide is boxed. The 7-aa long leader peptide contains mostly hydrophilic (shaded in orange) and neutral (no shading) residues, and it ends with a conserved Gly. This leader peptide is processed by the prepilin peptidase PilD, which is indicated by the vertical arrow, generating a protein of 454 residues (50.5 kDa). The processed protein starts with a tract of 21 predominantly hydrophobic residues (shaded in blue), which invariably form an extended α-helix that is the main assembly interface within filaments. The C-terminal vWA module (IPR036465) is boxed, with the conserved residues forming the MIDAS highlighted in yellow. Arrowheads indicate the proteins that were produced and purified in this study, consisting of either two modules (black arrowhead) or just the vWA module (red arrowhead). (B) Modular architectures of PilB and PilC minor pilins compared to the major pilins PilE1/PilE2. The proteins, from S. sanguinis 2908, have been drawn to scale. The black rounded rectangles correspond to the IPR012902 motif that is part of the class III signal peptide. The C-terminal domains in PilB and PilC are highlighted by colored rounded rectangles, vWA domain (red) and lectin domain (yellow).