Interactions Between Mastoparan B and the Membrane Studied by ^1H NMR Spectroscopy

다국어 초록 (Multilingual Abstract)

Mastoparan B (MP-B) is an antimicrobial cationic tetradecapeptide amide isolated from the venom of the hornet Vespa basalis. NMR spectroscopy was used to study the membrane associated structures of MP-B in various model membrane systems such as 120mM DPC micelles. 200mM SDS micelles, and 3% (w/v) DMPC/DHPC (1:2) bicelles. In all systems, MP-B has an amphiphilic α-helical structure from Lys^2-to Leu^14. NOESY experiments performed on MP-B in nondeuterated SDS micelles show that protons in the indole ring of Trp^9 are in close contact with methylene protons of SDS micelles. T_1 relaxation data and NOE data revealed that the bound form of MP-B may be dominant in SDS micelles. The interactions between MP-B and zwitterionic DPC micelles were much weaker than those between MP-B and anionic SDS micelles. By substitution of Trp^9 with Ala^9, the pore-forming activity of MP-B was decreased dramatically. All of these results imply that strong electrostatic interactions between the positively charged Lys residues in MP-B binding to the cell membrane. Then, insertion of the indole ring of Trp^9 into the membrane, as well as the amphiphilic α-helical structures of MP-B may allow MP-B to span the lipid bilayer through the C-terminal portion. These structural features are crucial for the potent antibiotic activities of MP-B.