Site-Directed Mutagenesis to Assess the Binding Capacityof Class S Protein ofStaphylococcus aureusLeucotoxins to the Surface of Polymorphonuclear Cells

[摘要] Staphylococcal leucotoxins result from the association of class Scomponents and class F component inducing the activation and thepermeabilization of the target cells. Likeα-toxin, theleucotoxins are pore-forming toxins with more than 70%β-sheet. This was confirmed by attenuated total reflectanceFourier transform infrared (ATR-FTIR) spectroscopy. In addition,threonine 28 of a predicted and conservedβ-sheet at theN-terminal extremity of class S proteins composing leucotoxinsaligns with histidine 35 ofα-toxin, which has a key rolein oligomerization of the final pore. Flow cytometry was used tostudy different aminoacid substitutions of the threonine 28 inorder to evaluate its role in the biological activity of theseclass S proteins. Finally, results show that threonine 28 of theleucotoxin probably plays a role similar to that of histidine 35ofα-toxin. Mutations on this threonin largely influencedthe secondary interaction of the class F component and led toinactive toxin.

[学科分类] 基础医学