Solid-state NMR structure determination of melittin in a lipid environment.
Solid-state (13)C NMR spectroscopy was used to investigate the three-dimensional structure of melittin as lyophilized powder and in ditetradecylphosphatidylcholine (DTPC) membranes. The distance between specifically labeled carbons in analogs [1-(13)C]Gly3-[2-(13)C]Ala4, [1-(13)C]Gly3-[2-(13)C]Leu6, [1-(13)C]Leu13-[2-(13)C]Ala15, [2-(13)C]Leu13-[1-(13)C]Ala15, and [1-(13)C]Leu13-[2-(13)C]Leu16 was measured by rotational resonance. As expected, the internuclear distances measured in [1-(13)C]Gly3-[2-(13)C]Ala4 and [1-(13)C]Gly3-[2-(13)C]Leu6 were consistent with alpha-helical structure in the N-terminus irrespective of environment. The internuclear distances measured in [1-(13)C]Leu13-[2-(13)C]Ala15, [2-(13)C]Leu13-[1-(13)C]Ala15, and [1-(13)C]Leu13-[2-(13)C]Leu16 revealed, via molecular modeling, some dependence upon environment for conformation in the region of the bend in helical structure induced by Pro14. A slightly larger interhelical angle between the N- and C-terminal helices was indicated for peptide in dry or hydrated gel state DTPC (139 degrees -145 degrees ) than in lyophilized powder (121 degrees -139 degrees ) or crystals (129 degrees ). The angle, however, is not as great as deduced for melittin in aligned bilayers of DTPC in the liquid-crystalline state (approximately 160 degrees ). The study illustrates the utility of rotational resonance in determining local structure within peptide-lipid complexes.
Lam
Y H
YH
School of Chemistry, University of Melbourne, Melbourne VIC 3010, Australia.
Wassall
S R
SR
Morton
C J
CJ
Smith
R
R
Separovic
F
F
D002247:Carbon Isotopes / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008555:Melitten / Q000138:chemical synthesis / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry; D008958:Models, Molecular; D010713:Phosphatidylcholines / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013816:Thermodynamics
D002247:Carbon Isotopes; D008051:Lipid Bilayers; D008055:Lipids; D008565:Membrane Proteins; D010713:Phosphatidylcholines; D008555:Melitten; D011392:Proline