Little is known about the organization of lipids in biomembranes. Lipid rafts are defined as
sphingolipid-and cholesterol-rich clusters in the membrane. Details of the lipid distribution of
lipid rafts are not well characterized mainly because of a lack of appropriate probes.
Ganglioside GM1-specific protein, cholera toxin, has long been the only lipid probe of lipid
rafts. Recently it was shown that earthworm toxin, lysenin, specifically recognizes
sphingomyelin-rich membrane domains. Binding of lysenin to sphingomyelin is …