Figure 2.

The cytolysin quorum-sensing system in E. faecalis. (A) The toxin structural components CylL_L (larger subunit) and CylL_S (smaller subunit) are encoded by cylL_L and cylL_S. CylL_L and CylL_S core peptides are post-translationally modified by CylM, after which these peptides are further processed and transported by CylB. Extracellular protease, CylA, removes six amino acid residues (leader peptide) from both CylL_L and CylL_S, making them active toxin subunits. The signal transduction mechanism linking the binding of extracellular CylL_S to CylR1 at the membrane with the dissociation of CylR2 from the P_L promoter is currently unknown. CylI provides self-immunity against cytolysin; (B) Structures of the CylL_L and CylL_S mature cytolysin subunits [82].