Discovery of a newNeisseria gonorrhoeaeType IV pilus assembly factor, TfpC

AbstractNeisseria gonorrhoeaerely on Type IV pili (T4p) to promote colonization of their human host and to cause the sexually transmitted infection, gonorrhea. This organelle cycles through a process of extension and retraction back into the bacterial cell. Through a genetic screen, we identified the NGO0783 locus ofN. gonorrhoeaestrain FA1090 as containing a gene encoding a protein required to stabilize the Type IV pilus in its extended, non-retracted conformation. We have named the genetfpCand the protein TfpC. Deletion oftfpCproduces a nonpiliated colony morphology and immuno-transmission electron microscopy confirms that the pili are lost in the ΔtfpCmutant, although there is some pilin detected near the bacterial cell surface. A copy of thetfpCgene expressed from alacpromoter restores pilus expression and related phenotypes. A ΔtfpCmutant shows reduced levels of pilin protein, but complementation with atfpCgene restored pilin to normal levels. Bioinformatic searches show there are orthologues in numerous bacteria species but not all Type IV pilin expressing bacteria contain orthologous genes. Co-evolution and NMR analysis indicates that TfpC contains an N-terminal transmembrane helix, a substantial extended/unstructured region and a highly charge C-terminal coiled-coil domain.ImportanceMost bacterial species express one or more extracellular organelles called pili/fimbriae that are required for many properties of each bacterial cell. TheNeisseria gonorrhoeaeType IV pilus is a major virulence and colonization factor for the sexually transmitted infection, gonorrhea. We have discovered a new protein ofNeisseria gonorrhoeaecalled TfpC that is required to maintain the Type IV pili on the bacterial cell surface. There are similar proteins found in the other members of theNeisseriagenus and many other bacterial species important for human health.