Streptolysin O possesses a single polypeptide chain with a molecular weight of f62 kDa. Streptolysin O binds to membrane cholesterol and oligomerizes to create a ring structure that consists
of 45 to 50 units. The ring structure inserts into the membrane to make a large pore (25 to 30 nm), which DNA, RNA, peptides and proteins may pass. It is thiol-activated. It is inhibited by
allicin, an active component of garlic.