Interaction between sterols and amphidinol 3 in lipid bilayers investigated by membrane-permeabilizing activities, surface plasmon resonance, and solid-state NMR

• Main Authors: Espiritu, Rafael Atillo, Matsumori, Nobuaki, Tsuda, Masashi, Murata, Michio
• Format: text
• Published: Animo Repository 2013
• Subjects: Dinoflagellates—Composition; Surface plasmon resonance; Nuclear magnetic resonance
• Online Access: https://animorepository.dlsu.edu.ph/faculty_research/5116
• Institution: De La Salle University

Marine dinoflagellates are rich source of biologically-active and structurally-unique secondary metabolites. Among those that show promising potential is pharmaceutically-relevant agents are antifungal amphidinols (AMs), a class of polyhydroxy polyene compounds isolated from Amphidium klebsii. To gain further insight the mechanism of sterol-recognition of AM3 in lipid bilayers, its activity in epicholesterol-containing membranes was assessed by calcein leakage. Results revealed that AM3 is devoid of membrane-permeabilizing activity in such liposomes indicating a probable stereoselective interaction with 3β-hydroxy group cholesterol. This preference towards the 3β-ol isomer likely results from a higher affinity with AM3 as was evidenced from surface plasmon resonance measurements. Reduction of the characteristic quadropolar splitting in solid-sate 2H NMR experiments using deuterated sterols (at the C3 position) showed that this increase in membrane affinity is brought about by direct intermolecular interaction between AM3 and 3β-hydroxysterols in membranes. However, similar spectral changes were also observed with deuterated epischolesterol, albeit less pronounced, indicating that AM3 may also recognize sterol backbone to a certain extent, but that pore formation requires the presence of the 3β-OH group. Additionally, solid state 31P NMR of cholesterol-containing POPC membranes in the presence of AM3 did not reveal isotropic signals, pointing to a possibility of permeabilization via formation of aggregates as in a barrel-stave pore.