Sterol-dependent membrane association of the marine sponge-derived bicyclic peptide Theonellamide A as examined by¹H NMR

• Main Authors: Cornelio, Kimberly, Espiritu, Rafael Atillo, Todokoro, Yasuto, Hanashima, Shinya, Kinoshita, Masanao, Matsumori, Nobuaki, Murata, Michio, Nishimura, Shinichi, Kakeya, Hideaki, Yoshida, Minoru, Matsunaga, Shigeki
• Format: text
• Published: Animo Repository 2016
• Subjects: Sponges; Cyclic peptides; Cholesterol; Chemistry
• Online Access: https://animorepository.dlsu.edu.ph/faculty_research/2672
• Institution: De La Salle University

Theonellamide A (TNM-A) is an antifungal bicyclic dodecapeptide isolated from a marine sponge Theonella sp. Previous studies have shown that TNM-A preferentially binds to 3β-hydroxysterol-containing membranes and disrupts membrane integrity. In this study, several1H NMR-based experiments were performed to investigate the interaction mode of TNM-A with model membranes. First, the aggregation propensities of TNM-A were examined using diffusion ordered spectroscopy; the results indicate that TNM-A tends to form oligomeric aggregates of 2–9 molecules (depending on peptide concentration) in an aqueous environment, and this aggregation potentially influences the membrane-disrupting activity of the peptide. Subsequently, we measured the1H NMR spectra of TNM-A with sodium dodecyl sulfate-d25(SDS-d25) micelles and small dimyristoylphosphatidylcholine (DMPC)-d54/dihexanoylphosphatidylcholine (DHPC)-d22bicelles in the presence of a paramagnetic quencher Mn2+. These spectra indicate that TNM-A poorly binds to these membrane mimics without sterol and mostly remains in the aqueous media. In contrast, broader1H signals of TNM-A were observed in 10 mol % cholesterol-containing bicelles, indicating that the peptide efficiently binds to sterol-containing bilayers. The addition of Mn2+to these bicelles also led to a decrease in the relative intensity and further line-broadening of TNM-A signals, indicating that the peptide stays near the surface of the bilayers. A comparison of the relative signal intensities with those of phospholipids showed that TNM-A resides in the lipid–water interface (close to the C2′ portion of the phospholipid acyl chain). This shallow penetration of TNM-A to lipid bilayers induces an uneven membrane curvature and eventually disrupts membrane integrity. These results shed light on the atomistic mechanism accounting for the membrane-disrupting activity of TNM-A and the important role of cholesterol in its mechanism of action. © 2016 Elsevier Ltd