Structure, Dynamics and Activity of the Antimicrobial Peptide Mastoparan-B Analogue studied by CD and NMR

• Main Authors: Wei-Cheng Tung, 童偉誠
• Other Authors: Chang-Shin Lee
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/27177084376712347903

碩士 === 淡江大學 === 化學學系碩士班 === 100 === Mastoparan B (MP-B) is an antimicrobial tetradecapeptide that was isolated from the hornet (Vespa basalis) venom with cationic character and the amidated C-terminus. We synthesized a MP-B analogue, N2Y9-MPB, mutated at position 2 and 9 with asparagine and tyrosine and investigated its antimicrobial activity, structure, and dynamics. Spectra of circular dichroism (CD) indicated that N2Y9-MPB convert from a random coil conformation in water to an α-helical structure in TFE and SDS micelles. Structure calculated via NMR data indicated the induced helix involves residues from 4 to 13 and 4 to 12 in 30% TFE at 283 K and 310 K, respectively, and from 4 to 13 in SDS micelles. The diffusion studies suggested that the peptide may form larger oligomers in TFE as temperature decreased from 310 K to 283 K. In aqueous TFE, the model-free analysis of 13C relaxation data showed that the order parameters, S2, in the helical segment are more restricted at both 310 K and 283 K. The NMR data showed that the orientation of Tyr9 and Lys11 in the micelle-bound conformation is different from that in 30% TFE. We propose that the positively charged Lys residues in N2Y9-MPB may firstly develop the electrostatic interactions with the negatively charged surface of SDS micelle, then the aromatic side chain of Tyr9 and the aliphatic side chain of Ile6 insert into the hydrophobic interior of the mimicking membranes. As well, we observed that the antimicrobial activity of N2Y9-MPB is relatively lower than MP-B, it may result from the mutant of Trp9 with Tyr and the mutant of Lys2 with Asn, which descend both the hydrophobic and the electrostatic interaction of N2Y9-MPB with membrane. Both interactions are fundamental in modulating the binding affinities of MP-B and its analogous with the anionic phospholipid layer of membranes.