Characterization of a glycan-binding complex of minor pilins completes the analysis of Streptococcus sanguinis type 4 pili subunits.
Shahin, M., Sheppard, D., Raynaud, C., Berry, J.L., Gurung, I., Silva, L.M., Feizi, T., Liu, Y., Pelicic, V.(2023) Proc Natl Acad Sci U S A 120: e2216237120-e2216237120
- PubMed: 36626560 
- DOI: https://doi.org/10.1073/pnas.2216237120
- Primary Citation of Related Structures:  
7O5Y, 7OA7, 7OA8 - PubMed Abstract: 
Type 4 filaments (T4F)-of which type 4 pili (T4P) are the archetype-are a superfamily of nanomachines nearly ubiquitous in prokaryotes. T4F are polymers of one major pilin, which also contain minor pilins whose roles are often poorly understood. Here, we complete the structure/function analysis of the full set of T4P pilins in the opportunistic bacterial pathogen Streptococcus sanguinis . We determined the structure of the minor pilin PilA, which is unexpectedly similar to one of the subunits of a tip-located complex of four minor pilins, widely conserved in T4F. We found that PilA interacts and dramatically stabilizes the minor pilin PilC. We determined the structure of PilC, showing that it is a modular pilin with a lectin module binding a subset of glycans prevalent in the human glycome, the host of S. sanguinis . Altogether, our findings support a model whereby the minor pilins in S. sanguinis T4P form a tip-located complex promoting adhesion to various host receptors. This has general implications for T4F.
Organizational Affiliation: 
Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, SW7 2AZ London, United Kingdom.