title: 2NH and 3OH are crucial structural requirements in sphingomyelin for sticholysin II binding and pore formation in bilayer membranes.
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 StnII failed to bind to bilayers containing methylated SM-analogs, whereas clear binding was seen to SM-containing bilayers. StnII 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.
authors: Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland.
authors: Terhi
authors: T
authors: Maula
authors: Y Jenny E
authors: YJ
authors: Isaksson
authors: Sara
authors: S
authors: García-Linares
authors: Sanna
authors: S
authors: Niinivehmas
authors: Olli T
authors: OT
authors: Pentikäinen
authors: Mayuko
authors: M
authors: Kurita
authors: Shou
authors: S
authors: Yamaguchi
authors: Tetsuya
authors: T
authors: Yamamoto
authors: Shigeo
authors: S
authors: Katsumura
authors: José G
authors: JG
authors: Gavilanes
authors: Alvaro
authors: A
authors: Martínez-del-Pozo
authors: J Peter
authors: JP
authors: Slotte
mesh_terms: D000818:Animals; D001665:Binding Sites; D002151:Calorimetry; D003064:Cnidarian Venoms / Q000737:chemistry* / Q000378:metabolism; D003198:Computer Simulation; D006860:Hydrogen Bonding; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D052899:Pore Forming Cytotoxic Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012615:Sea Anemones / Q000737:chemistry / Q000378:metabolism; D013109:Sphingomyelins / Q000737:chemistry* / Q000378:metabolism; D020349:Surface Plasmon Resonance; D053835:Unilamellar Liposomes / Q000737:chemistry* / Q000378:metabolism
chemical_list: D003064:Cnidarian Venoms; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D052899:Pore Forming Cytotoxic Proteins; D013109:Sphingomyelins; D053835:Unilamellar Liposomes; C404794:sticholysin II; C028694:1-palmitoyl-2-oleoylphosphatidylcholine