ANALYSIS OF PROTEIN-BINDING TO THE SMA CLA DNA REPEAT IN PATHOGENIC NEISSERIAE/

Antigenic variation of the pilus is an essential component of Neisseri a gonorrhoeae pathogenesis. Unidirectional recombination of silent pil in DNA into an expressed pilin gene allows for substantial sequence va riation of this highly immunogenic surface structure. While the RecA p rotein is required for pilin gene recombination, the factors which mai ntain the silent reservoir of pilin sequences and/or allow unidirectio nal recombination from silent to expression loci remain undefined, We have previously shown that a conserved sequence at the 3' end of all p ilin loci (the Sma/Cla repeat) is required to be present at the expres sion locus for efficient recombination from the silent loci, In this s tudy, the binding of gonococcal proteins to this DNA sequence was inve stigated, Gel mobility shift assays and competition experiments using deletion derivatives of the repeat, show that multiple activities bind to different regions of the Sma/Cla repeat and define the boundaries of the binding sequences, Moreover, only the pathogenic Neisseria harb or proteins which specifically bind to this repeat, suggesting a corre lation between the expression of these DNA binding proteins and the po tential to cause disease.