title: Axial hydrogen at C7 position and bumpy tetracyclic core markedly reduce sterol's affinity to amphotericin B in membrane.
abstract: The interaction of amphotericin B (AmB) with fungal ergosterol (Erg) is stronger than its interaction with mammalian cholesterol (Cho), and this property of AmB as an antifungal drug is thought to be responsible for its selective toxicity toward fungi. However, the mechanism by which AmB recognizes the structural differences between sterols, particularly minor difference in the sterol alicyclic portion, is largely unknown. Thus, to investigate the mode of interaction between AmB and the sterol core, we assessed the affinity of AmB to various sterols with different alicyclic structures. Ion flux assays and UV spectral measurements clearly revealed the importance of the Δ7-double bond of the sterol B-ring for interaction with the drug. AmB showed lower affinity for triene sterols, which have double bonds at the Δ5, Δ7, and Δ9 positions. Intermolecular distance measurements by (13)C{(19)F} rotational echo double resonance (REDOR) revealed that the AmB macrolide ring is in closer contact with the steroid core of Erg than it is with the Cho core in the membrane. Conformational analysis suggested that an axial hydrogen atom at C7 of Δ5-sterol (2, 6) and the protruded A-ring of Δ5,7,9-sterol (4, 8) sterically hampered face-to-face contact between the van der Waals surface of the sterol core and the macrolide of AmB. These results further suggest that the α-face of sterol alicycle interacts with the flat macrolide structure of AmB.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University , 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nakagawa
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Umegawa
authors.forename: Kenichi
authors.initials: K
authors.lastname: Nonomura
authors.forename: Naohiro
authors.initials: N
authors.lastname: Matsushita
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Takano
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tsuchikawa
authors.forename: Shinya
authors.initials: S
authors.lastname: Hanashima
authors.forename: Tohru
authors.initials: T
authors.lastname: Oishi
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Matsumori
authors.forename: Michio
authors.initials: M
authors.lastname: Murata
mesh_terms: D000666:Amphotericin B / Q000737:chemistry* / Q000494:pharmacology*; D000935:Antifungal Agents / Q000737:chemistry* / Q000494:pharmacology*; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D005658:Fungi / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D009181:Mycoses / Q000188:drug therapy / Q000382:microbiology; D013261:Sterols / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000935:Antifungal Agents; D008081:Liposomes; D013261:Sterols; D000666:Amphotericin B