May influence the kinetics of pilus outgrowth and/or retraction (PubMed:1355084). Overexpression phenocopies the deletion mutation; i.e. causes resistance to F-pilus-specific phage and CdiA-CT toxin (PubMed:24889811). Expresses approximately normal numbers of F pili that are unusually long, remains plasmid transfer proficient, displays increased resistance to F-pilus-specific phage (PubMed:1355084). Resistant to phage R17 and M13, conjugates at lower efficiency (about 10% of wild-type), resistant to CdiA-CT toxin (PubMed:24889811).