CHEMICAL FATTY ACYLATION CONFERS HEMOLYTIC AND TOXIC ACTIVITIES TO ADENYLATE-CYCLASE PROTOXIN OF BORDETELLA-PERTUSSIS

Adenylate cyclase toxin (ACT), a virulence factor of Bordetella pertus sis, acquires hemolytic and toxic activities after post-translational modification of the cyaA gene product, CyaA. The exact nature of this modification is unknown, but homology to the related repeat toxin cu-h emolysin of Escherichia coil suggests that fatty acylation of a lysine residue may be involved, In the present study, we used an in, vitro c hemical approach to acylate unmodified, inactive adenylate cyclase pro toxin by using a new water soluble compound, acylpyrophosphate. We sho w that undirected transfer of lauric, myristic, or palmitic acid chain s to the CyaA protoxin is able to confer both hemolytic and toxic acti vities to ACT. The chemically modified protoxin shows a specific requi rement for Ca2+ ions for toxic activity, as does the wild type toxin. However, the toxic and hemolytic activities of chemically modified ACT are low in comparison to ACT modified in vivo, suggesting that in vit ro fatty acylation of the protoxin involves random modification of nuc leophilic residues present in the toxin in contrast to the in vivo mod ification of specific sites.