Open AccessStructural elements of the cholesterol-dependent cytolysins that are responsible for their cholesterol-sensitive membrane interactions
Author(s) -
Casie E. Soltani,
Eileen M. Hotze,
Arthur E. Johnson,
Rodney K. Tweten
Publication year - 2007
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0708104105
Subject(s) - membrane , biophysics , chemistry , cysteine , cell membrane , cholesterol , membrane protein , biochemistry , biology , enzyme
The pore-forming mechanism of the cholesterol-dependent cytolysins (CDCs) exhibits an absolute requirement for membrane cholesterol. The structural elements of the CDCs that mediate this interaction are not well understood. Three short hydrophobic loops (L1–L3) and a highly conserved undecapeptide sequence at the tip of domain 4 of the CDC structure are known to anchor the CDC to the membrane. It has been thought that the undecapeptide directly mediates the interaction of the CDCs with a cholesterol-rich cell surface. Herein we show that the L1–L3 loops, not the undecapeptide, are responsible for mediating the specific interaction of the CDCs with cholesterol-rich membranes. The membrane insertion of the undecapeptide was uncoupled from membrane binding by the covalent modification of the undecapeptide cysteine thiol. Modification of the cysteine prevented prepore to pore conversion, but did not affect membrane binding, thus demonstrating that undecapeptide membrane insertion follows that of the L1–L3 loops. These studies provide an example of a structural motif that specifically mediates the interaction of a bacterial toxin with a cholesterol-rich membrane.