The meningococcal gene (encoding factor H binding protein) is naturally expressed from two independent transcripts by two differentially regulated promoters. In one transcript it is co-expressed with the neighbouring upstream gene from the P promoter. The other transcript is monocistronic and is expressed from its own dedicated promoter, P, which is activated by the global regulatory protein FNR in response to oxygen-limiting conditions. To increase expression of the monocistronic transcript a constitutively-active FNR mutant is used. The Ppromoter can thus be activated, leading to over-expression of FNR-activated genes, such as
