A large number of antimicrobial peptides (AMPs) act with high selectivity and specificity through interactions with membrane lipid components. These peptides undergo complex conformational changes in solution; upon binding to an interface, one major conformation is stabilized. A recent publication by researchers from Federal University de Janeiro describe the interaction between tritrpticin (TRP3), a cathelicidin AMP, and micelles of different chemical composition.

The peptide’s structure and dynamics were examined using one-dimensional and two-dimensional NMR. Their data showed that the interaction occurred by conformational selection and the peptide acquired similar structures in all systems studied, despite differences in detergent headgroup charge or dipole orientation. Fluorescence and paramagnetic relaxation enhancement experiments showed that the peptide is located in the interface region and is slightly more deeply inserted in 1-myristoyl-2-hydroxy-sn-glycero-3-phospho-1′-rac-glycerol (LMPG, anionic) than in 1-lauroyl-2-hydroxy-sn-glycero-3-phosphocholine (LLPC, zwitterionic) micelles. Moreover, the tilt angle of an assumed helical portion of the peptide is similar in both systems.

In previous work these researchers proposed that TRP3 acts by a toroidal pore mechanism. In view of the high hydrophobic core exposure, hydration, and curvature presented by micelles, the conformation of TRP3 in these systems could be related to the peptide’s conformation in the toroidal pore.

toroid

 

Reference
T. L. Santos, A. Moraes, C. R. Nakaie, F. C.L. Almeida, S. Schreier, A. P. Valente (2017) Structural and Dynamic Insights of the Interaction between Tritrpticin and Micelles: An NMR Study Biophysical Journal 111(12) pp 2676-2688. doi: 10.1016/j.bpj.2016.10.034 [abstract]

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