A polymorphic regulation system in Staphylococcus aureus.

The synthesis of virulence factors of Staphylococcus aureus is regulated by the accessory gene regulator system (agr) which involves a quorum sensing mechanism. Accumulation of an autoinducing peptide (AIP), encoded by agr, in the extracellular environment leads to the stimulation of a two components signal transduction system: AgrC (receptor) and AgrA (response regulator). Three alleles of the agr system have already been identified in S, aureus. In each allele, the autoinducing peptide induces a specific stimulation of AgrC belonging to the same allele and inhibits the AgrC receptors of all other alleles. Modeling the interactions between the autoinducing peptide and AgrC could contribute to a better understanding of the structure-activity relationships and could lead to the synthesis of agr system inhibiting peptides. Such peptides would offer the advantage of decreasing the virulence of pathogenic staphylococci strains with minor effects on the ecological balance. (C) 2000 Editions scientifiques et medicales Elsevier SAS.