Two residues in Staphylococcus aureus alpha-hemolysin related to hemolysis and self-assembly Yufeng Du,1 Li Liu,2 Chunping Zhang,3 Yani Zhang1 1College of Life Sciences, Northwest University, Xi’an 710069, China; 2Ultrasonic Diagnosis Department, Shaanxi Provincial People’s Hospital, Xi’an 710068, China; 3College of Chemistry and Material Science, Northwest University, Xi’an 710069, China Abstract: Staphylococcus aureus is becoming increasingly intractable because of its ability to acquire antimicrobial resistance and secrete numerous virulence factors that can exacerbate inflammation. Alpha-hemolysin (Hla) is a pore-forming virulence factor produced by S. aureus that can self-assemble into heptameric mushroom-structured pores in target cell membranes, leading to cell lysis and death. In the present study, we sought to better understand the mechanism underlying hemolysis and the oligomerization of Hla by creating nine mutants with single amino acid changes in different positions of the Hla protein: N17C, T18C, P103C, N105C, M113C, T117C, N121C, D128C, and T129C. The results showed that the P103C and N105C mutations, which are located in the triangle region, significantly diminished hemolysis and heptamer formation when compared with the wild-type Hla protein. This suggests that the P103 and N105 residues play key roles in the assembly of the Hla pore. These results improve our understanding of the mechanism underlying the pore-forming ability of Hla. Keywords: α-hemolysin, hemolysis, heptamer oligomers, cysteine mutants, assembly