Solid-state NMR and simulation studies of equinatoxin II N-terminus interaction with lipid bilayers.
The interaction with model membranes of a peptide, EqtII(1-32), corresponding to the N-terminal region of the pore-forming toxin equinatoxin II (EqtII) has been studied using solid-state NMR and molecular dynamics (MD) simulations. The distances between specifically labeled nuclei in [(19)F-para]Phe16-[1-(13)C]Leu19 and [(19)F-para]Phe16-[(15)N]Leu23 analogs of EqtII(1-32) measured by REDOR in lyophilized peptide were in agreement with published crystal and solution structures. However, in both DMPC and mixed DMPC:SM membrane environments, significant changes in the distances between the labeled amino acid pairs were observed, suggesting changes in helical content around the experimentally studied region, 16-23, in the presence of bilayers. (19)F-(31)P REDOR experiments indicated that the aromatic ring of Phe16 is in contact with lipid headgroups in both membrane environments. For the DMPC:SM mixed bilayers, a closer interaction between Phe16 side chains and lipid headgroups was observed, but an increase in distances was observed for both labeled amino acid pairs compared with those measured for EqtII(1-32) in pure DMPC bilayers. The observed differences between DMPC and DMPC:SM bilayers may be due to the greater affinity of EqtII for the latter. MD simulations of EqtII(1-32) in water, on a pure DMPC bilayer, and on a mixed DMPC:SM bilayer indicate significant peptide secondary structural differences in the different environments, with the DMPC-bound peptide adopting helical formations at residues 16-24, whereas the DMPC:SM-bound peptide exhibits a longer helical stretch, which may contribute to its enhanced activity against PC:SM compared with pure PC bilayers. Proteins 2010. (c) 2009 Wiley-Liss, Inc.
Biomembrane Structure Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom.
Yuen Han
YH
Lam
Andrew
A
Hung
Raymond S
RS
Norton
Frances
F
Separovic
Anthony
A
Watts
D003064:Cnidarian Venoms / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D056004:Molecular Dynamics Simulation; D010446:Peptide Fragments / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D017433:Protein Structure, Secondary; D013109:Sphingomyelins / Q000737:chemistry; D013499:Surface Properties
D003064:Cnidarian Venoms; D008051:Lipid Bilayers; D010446:Peptide Fragments; D010713:Phosphatidylcholines; D013109:Sphingomyelins; C012307:equinatoxin