The thiol-activated Cholesterol-dependent Cytolysin (CDC) family (TC# 1.C.12) is a member of the MACPF superfamily. Cholesterol dependent cytolysins are a family of β-barrel pore-forming exotoxins that are secreted by gram-positive bacteria. CDCs are secreted as water-soluble monomers of 50-70 kDa, that when bound to the target cell, form a circular homo-oligomeric complex containing as many as 40 (or more) monomers. Through multiple conformational changes, the β-barrel transmembrane structure (~250 Å in diameter depending on the toxin) is formed and inserted into the target cell membrane. The presence of cholesterol in the target membrane is required for pore formation, though the presence of cholesterol is not required by all CDCs for binding. For example, intermedilysin (ILY; TC# 1.C.12