Inhibitory Effect And Mechanism Of Acacetin On Staphylococcus Aureus Sortase A

Staphylococcus aureus(S. aureus) is a medically-important pathogen of avariety of human infections, which is notorious for its ability to acquire resistance to the commonly used antimicrobial agents. The inexorable onslaught by antibiotic-resistant S. aureus that continues to threaten human health presents an urgent need for novel therapeutic approaches that do not exert selective pressure on evolutionary adaptation of the bacteria. An alternative approach is to develop anti-virulence therapies that interfere with bacterial virulence determinants or pathways that mediate virulence. Sortase A(Srt A) of S. aureus, which is seen as the archetypal sortase, has been shown to be essential for pathogenesis and has therefore received much attention as a potential target for novel therapeutics. Srt A is responsible for binding a number of surface proteins associated with virulence to the cell wall. Therefore, inhibition of the activity of Srt A could lead to an attenuation of the virulence of S.aureus.In this study, based on the fluorescence resonance energy transfer(FRET) assay, we screened Acacetin as the most effective inhibitor from some natural compounds which do not influence the growth of S. aureus. Furthermore, the bacterial growth curve was drawn to determine Acacetin couldn’t influence the growth of S.aureus. The fibrinogen-binding assay and Sp A-associated fluorescence analysis were performed to illustrate Acacetin could cripple the adhesion of S.aureus and reduce the expression of Sp A on the cell wall of S.aureus. Based on the analysis by molecular docking and dynamic simulation, Acacetin adopted a compact conformation binding at the pocket of the Srt A and binded to the active region of Srt A(Arg-139 and Lys-140). The renal abscess model of mice was constructed to study the protection and treatment function of Acacetin on mice infected by S.aureus. The results show that Acacetin could lead to an attenuation of the virulence of S.aureus, improved the survival rate of mice, reduced the formation of renal abscess, protected and treated the mice infected by S.aureus.Taken all together, these findings indicated that Acacetin has the potential to be a leading compound for the development of anti-virulence agents against S. aureus infections via inhibiting the activity of Srt A. It provides an important structural basis for the design and development of new drugs.