The presence of type IV pili can be correlated with virulence in many Gram-negative bacteria that inhabit mucosal surfaces of man. The expression of these proteinaceous appendages by Neisseria gonorrhoeae, the causative agent of gonorrhea, appears to play an essential role in the pathogenesis of gonococcal disease. An analogous association between type IV pilus expression and virulence can be made for N. meningitidis, the etiologic agent of epidemic meningitis, Vibrio cholerae, the agent of cholera, and for enteropathogenic strains of Escherichia coli. Together, these bacterial pathogens are responsible for extensive morbidity and mortality worldwide. However, the precise role of type IV pili in promoting infectivity remains unclear. The long term objectives of this proposal are to understand the processes of pilus assembly in N. gonorrhoeae at the molecular level, with one goal being the development of treatments and prophylactic regimens that intervene in the infectious process by disrupting organelle biosynthesis and function. In previous work, genes and products that are essential to organelle assembly have been identified. These gonococcal pilus assembly components are highly related to those required for toxin secretion by diverse human pathogens, including Vibrio cholerae, Pseudomonas aeruginosa, and Bordetella pertussis. The Specific Aims are to: 1) Characterize the genetic organization and patterns of transcription of the pilus assembly genes; 2) Determine the subcellular locations and levels of expression of the pilus assembly gene products; 3) Investigate the patterns of pilin processing and localization in assembly mutants; and 4) Use regulated expression of assembly genes in studies of pilus biogenesis.