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- Title
A kinked antimicrobial peptide from Bombina maxima. II. Behavior in phospholipid bilayers.
- Authors
Heinzmann, Ralf; Grage, Stephan; Schalck, Constantin; Bürck, Jochen; Bánóczi, Zoltán; Toke, Orsolya; Ulrich, Anne
- Abstract
The preceding contribution by Toke et al. has studied the structure of the cationic antimicrobial peptide maximin-4 in detergent micelles and in organic solvent, revealing a different kink angle and side-chain interactions in the two different environments. Here, we have examined the same peptide in lipid bilayers using oriented circular dichroism (OCD) and solid-state N nuclear magnetic resonance (NMR) in aligned samples. OCD showed that maximin-4 is helical and adopts an oblique alignment in the membrane, and lacks the characteristic realignment response that is often observed for amphipathic α-helical peptides at a peptide:lipid ratio between 1:100 and 1:20. Solid-state N-NMR experiments suggest that maximin-4 also remains unaffected by lipid charge and temperature. Analyzing N labels in positions Ala12, Ala13, and Leu14, an oblique tilt angle of the N-terminal helix of ~130° relative to the membrane normal was found, in good agreement with the amphiphilic profile of this segment. An additional constraint at Ala22 in the C-terminal segment is found to be compatible with a continuous α-helix, but unfavorable side-chain interactions make this solution unlikely. Instead, a kink at Gly16 seems fully compatible with all known constraints and with the biophysical expectations in the membrane-bound state, given the liquid-state NMR structures. It thus seems that the flexible kink in maximin-4 allows the two helical segments to adjust to the local environment. The irregular amphiphilic profile and the resulting versatility in shape might explain why maximin-4 lacks the realignment response that has been characteristically observed for many related frog peptides forming straight amphipathic α-helices.
- Subjects
ANTIMICROBIAL peptides; BOMBINA; BILAYER lipid membranes; NUCLEAR magnetic resonance; ORGANIC solvents; CIRCULAR dichroism; BIOPHYSICS
- Publication
European Biophysics Journal, 2011, Vol 40, Issue 4, p463
- ISSN
0175-7571
- Publication type
Article
- DOI
10.1007/s00249-010-0668-x