Cholesterol‐dependent cytolysins: The outstanding questions

The cholesterol‐dependent cytolysins (CDCs) are a major family of bacterial pore‐forming proteins secreted as virulence factors by Gram‐positive bacterial species. CDCs are produced as soluble, monomeric proteins that bind specifically to cholesterol‐rich membranes, where they oligomerize into ring‐shaped pores of more than 30 monomers. Understanding the details of the steps the toxin undergoes in converting from monomer to a membrane‐spanning pore is a continuing challenge. In this review we summarize what we know about CDCs and highlight the remaining outstanding questions that require answers to obtain a complete picture of how these toxins kill cells.