Perturbing the acetylation status of the Type IV pilus retraction motor, PilT, reduces Neisseria gonorrhoeae viability

• Published in: Molecular microbiology Vol. 110; no. 5; pp. 677 - 688
• Main Authors: Hockenberry, Alyson M., Post, Deborah M. B., Rhodes, Katherine A., Apicella, Michael, So, Magdalene
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.12.2018
• Subjects: Acetylation; Females; Genetic transformation; Lethality; Lysine; Motors; Mutation; Neisseria gonorrhoeae; Proteins; Ultrastructure; Viability
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.13979

Summary Post‐translational acetylation is a common protein modification in bacteria. It was recently reported that Neisseria gonorrhoeae acetylates the Type IV pilus retraction motor, PilT. Here, we show recombinant PilT can be acetylated in vitro and acetylation does not affect PilT ultrastructure. To investigate the function of PilT acetylation, we mutated an acetylated lysine, K117, to mimic its acetylated or unacetylated forms. These mutations were not tolerated by wild‐type N. gonorrhoeae, but they were tolerated by N. gonorrhoeae carrying an inducible pilE when grown without inducer. We identified additional mutations in pilT and pilU that suppress the lethality of K117 mutations. To investigate the link between PilE and PilT acetylation, we found the lack of PilE decreases PilT acetylation levels and increases the amount of PilT associated with the inner membrane. Finally, we found no difference between wild‐type and mutant cells in transformation efficiency, suggesting neither mutation inhibits Type IV pilus retraction. Mutant cells, however, form microcolonies morphologically distinct from wt cells. We conclude that interfering with the acetylation status of PilTK117 greatly reduces N. gonorrhoeae viability, and mutations in pilT, pilU and pilE can overcome this lethality. We discuss the implications of these findings in the context of Type IV pilus retraction regulation. Cells can control protein activity through post‐translational modification. Here, we show by genetic analysis that the viability of pathogen Neisseria gonorrhoeae is dramatically reduced when its PilT protein is prevented from switching between acetylated and deacetylated states. Loss of viability is overcome when secondary mutations occur in genes encoding proteins known or suspected to interact with PilT at the membrane. These findings demonstrate that acetylation is an important determinant of PilT function, and imply that PilT influences membrane dynamics.