Effect of sphingomyelin and cholesterol on the interaction of St II with lipidic interfaces.
Sticholysin II (St II) is a cytolysin produced by the sea anemone Stichodactyla helianthus, characterized by forming oligomeric pores in natural and artificial membranes. In the present work the influence of the membrane lipidic components sphingomyelin (SM) and cholesterol (Cho) on binding and functional activity of St II, was evaluated using ELISA, lipid monolayers and liposomes. The aim of this work was to establish the promoting role of Cho and SM, both in St II binding and pore formation efficiency. In general the association (evaluated by ELISA and incorporation to phospholipid monolayers) of St II to lipids mixtures was better than to any one of the single components. Regarding the unique role of SM, it was found that, albeit inefficiently, St II binds to phosphatidylcholine (PC):Cho monolayers and liposomes, and is able to form active pores in these bilayers. The results in monolayers and liposomes show that the presence of SM and large amounts of Cho leads to the highest values of critical pressure and rate of association to monolayers, the most favorable interaction with liposomes, and the fastest rate of pore formation, in spite of the rigidity of the layers as suggested by the high generalized polarization (GP) of Laurdan incorporated to liposomes and FTIR data. Taken together, the present results show that the joint presence of SM and Cho, both in binary and ternary (PC containing) mixtures provide conditions particularly suitable for St II binding and function. We suggest that microdomains present in the bilayers could be important for toxin-membrane association.
Martínez
Diana
D
Facultad de Biología, Universidad de la Habana, Centro de Estudio de Proteínas, Calle 25 no 455, CP 10400, Cuba. dmcb@fbio.uh.cu
Otero
Anabel
A
Alvarez
Carlos
C
Pazos
Fabiola
F
Tejuca
Mayra
M
Lanio
María Eliana
ME
Gutiérrez-Aguirre
Ion
I
Barlic
Ariana
A
Iloro
Ibon
I
Arrondo
Jose Luis
JL
González-Mañas
Juan Manuel
JM
Lissi
Eduardo
E
D000818:Animals; D002784:Cholesterol / Q000494:pharmacology*; D003064:Cnidarian Venoms / Q000494:pharmacology*; D004347:Drug Interactions; D004797:Enzyme-Linked Immunosorbent Assay; D008081:Liposomes / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism*; D011485:Protein Binding; D012615:Sea Anemones; D013109:Sphingomyelins / Q000494:pharmacology*
D003064:Cnidarian Venoms; D008081:Liposomes; D008563:Membrane Lipids; D013109:Sphingomyelins; C404794:sticholysin II; D002784:Cholesterol