What is true about α-hemolysin?

The correct choice highlights that α-hemolysin assembles to form pores in cell membranes. This is a key characteristic of α-hemolysin, which is a pore-forming toxin produced by certain strains of Staphylococcus aureus. Once secreted, these proteins typically oligomerize (assemble into larger structures) in the membrane of target cells, allowing the formation of channels or pores. This pore formation disrupts the integrity of the cell membrane, leading to cell lysis and contributing to the pathogenicity of the bacteria.

Understanding the other options provides further clarity on the nature of α-hemolysin. It is not secreted as a dimer, but rather forms larger oligomeric structures which create the complete pore structure necessary for its function. Additionally, α-hemolysin does interact with lipid bilayers and specifically requires them to form the pores effectively; this makes its action quite dependent on the presence of membranes. Lastly, α-hemolysin is not a part of the cytoplasmic membrane; it operates from the outside by binding to and creating pores in the membranes of host cells.