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. 1999 Dec;77(6):3152–3155. doi: 10.1016/S0006-3495(99)77145-6

Orientation of cecropin A helices in phospholipid bilayers determined by solid-state NMR spectroscopy.

F M Marassi 1, S J Opella 1, P Juvvadi 1, R B Merrifield 1
PMCID: PMC1300585  PMID: 10585936

Abstract

The orientation of the insect antibiotic peptide cecropin A (CecA) in the phospholipid bilayer membrane was determined using (15)N solid-state NMR spectroscopy. Two peptide samples, each specifically labeled with (15)N at Val(11) or Ala(27), were synthesized by solid phase techniques. The peptides were incorporated into phospholipid bilayers, prepared from a mixture of dimyristoylphosphatidylcholine and dimyristoylphosphatidylglycerol, and oriented on glass slides. The (15)N chemical shift solid-state NMR spectra from these uniaxially oriented samples display a single (15)N chemical shift frequency for each labeled residue. Both frequencies are near the upfield end of the (15)N chemical shift powder pattern, as expected for an alpha-helix with its long axis in the plane of the membrane and the NH bonds perpendicular to the direction of the magnetic field. These results support a mechanism of action in which CecA binds to and covers the membrane surface, thereby causing a general destabilization and leakiness of the lipid bilayer membrane. The data are discussed in relation to a proposed mechanism of membrane lysis and bacterial killing via an ion channel activity of CecA.

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Selected References

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