2NH and 3OH are crucial structural requirements in sphingomyelin for sticholysin II binding and pore formation in bilayer membranes

T Maula, Jenny Isaksson, S Garcia-Linares, S Niinivehmas, OT Pentikainen, M Kurita, S Yamaguchi, T Yamamoto, S Katsumura, JG Gavilanes, A Martinez-del-Pozo, JP Slotte

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    Abstract

    Sticholysin II (StnII) is a pore-forming toxin from the sea anemone Stichodactyla heliantus which belongs to the large actinoporin family. The toxin binds to sphingomyelin (SM) containing membranes, and shows high binding specificity for this lipid. In this study, we have examined the role of the hydrogen bonding groups of the SM long-chain base (i.e., the 2NH and the 3OH) for StnII recognition. We prepared methylated SM-analogs which had reduced hydrogen bonding capability from 2NH and 3OH. Both surface plasmon resonance experiments, and isothermal titration calorimetry measurements indicated that Stall failed to bind to bilayers containing methylated SM-analogs, whereas clear binding was seen to SM-containing bilayers. Stall also failed to induce calcein release (i.e., pore formation) from vesicles made to contain methylated SM-analogs, but readily induced calcein release from SM-containing vesicles. Molecular modeling of SM docked to the phosphocholine binding site of StnII indicated that the 2NH and 3OH groups were likely to form a hydrogen bond with Tyr135. In addition, it appeared that Tyr111 and Tyr136 could donate hydrogen bonds to phosphate oxygen, thus stabilizing SM binding to the toxin. We conclude that the interfacial hydrogen bonding properties of SM, in addition to the phosphocholine head group, are crucial for high-affinity SM/StnII-interaction. (C) 2013 Elsevier B.V. All rights reserved.
    Original languageUndefined/Unknown
    Pages (from-to)1390–1395
    Number of pages6
    JournalBBA - Biomembranes
    Volume1828
    Issue number5
    DOIs
    Publication statusPublished - 2013
    MoE publication typeA1 Journal article-refereed

    Keywords

    • Isothermal titration calorimetry
    • Membrane permeabilization
    • Molecular docking
    • Surface plasmon resonance

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