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Structural Requirements of Cholesterol for Binding to Vibrio cholerae Hemolysin
Author(s) -
Ikigai Hajime,
Otsuru Hiroshi,
Yamamoto Koichiro,
Shimamura Tadakatsu
Publication year - 2006
Publication title -
microbiology and immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 70
eISSN - 1348-0421
pISSN - 0385-5600
DOI - 10.1111/j.1348-0421.2006.tb03848.x
Subject(s) - oligomer , monomer , sterol , vibrio cholerae , ergosterol , chemistry , stereochemistry , cholesterol , biochemistry , biology , polymer chemistry , organic chemistry , bacteria , genetics , polymer
Cholesterol is necessary for the conversion of Vibrio cholerae hemolysin (VCH) monomers into oligomers in liposome membranes. Using different sterols, we determined the stereochemical structures of the VCH‐binding active groups present in cholesterol. The VCH monomers are bound to cholesterol, diosgenin, campesterol, and ergosterol, which have a hydroxyl group at position C‐3 (3βOH) in the A ring and a C–C double bond between positions C‐5 and C‐6 (C–C Δ 5 ) in the B ring. They are not bound to epicholesterol and dihydrocholesterol, which form a covalent link with a 3αOH group and a C–C single bond between positions C‐5 and C‐6, respectively. This result suggests that the 3βOH group and the C–C Δ 5 bond in cholesterol are required for VCH monomer binding. We further examined VCH oligomer binding to cholesterol. However, this oligomer did not bind to cholesterol, suggesting that the disappearance of the cholesterol‐binding potential of the VCH oligomer might be a result of the conformational change caused by the conversion of the monomer into the oligomer. VCH oligomer formation was observed in liposomes containing sterols with the 3βOH group and the C–C Δ 5 bond, and it correlated with the binding affinity of the monomer to each sterol. Therefore, it seems likely that monomer binding to membrane sterol leads to the assembly of the monomer. However, since oligomer formation was induced by liposomes containing either epicholesterol or dihydrocholesterol, the 3βOH group and the C–C Δ 5 bond were not essential for conversion into the oligomer.