Phospholipid flip-flop modulated by transmembrane peptides WALP and melittin

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• 作者：Timothy C. Anglin ; Krystal L. Brown ; John C. Conboy
• 关键词：SFVS ; Flip-flop ; Melittin ; WALP ; Thermodynamics
• 刊名：Journal of Structural Biology
• 出版年：2009
• 期刊代码：92_10478477
• 类别：ph
• 出版时间：October 2009
• 卷：168
• 期：1
• 页码：37-52
• 文件大小：885 K

摘要

Select transmembrane proteins found in biogenic membranes are known to facilitate rapid bidirectional flip-flop of lipids between the membrane leaflets, while others have no little or no effect. The particular characteristics which determine the extent to which a protein will facilitate flip-flop are still unknown. To determine if the relative polarity of the transmembrane protein segment influences its capacity for facilitation of flip-flop, we have studied lipid flip-flop dynamics for bilayers containing the peptides WALP₂₃ and melittin. WALP₂₃ is used as a model hydrophobic peptide, while melittin consists of both hydrophobic and hydrophilic residues. Sum-frequency vibrational spectroscopy (SFVS) was used to characterize the bilayers and determine the kinetics of flip-flop for the lipid component, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), within the mixed bilayers. The kinetic data were utilized to determine the activation thermodynamics for DSPC flip-flop in the presence of the peptides. Melittin was found to significantly reduce the free energy barrier to DSPC flip-flop when incorporated into the bilayer at 1 mol.%, while incorporation of WALP₂₃ at the same concentration led to a more modest reduction of the free energy barrier. The possible mechanisms by which these peptides facilitate flip-flop are analyzed and discussed in terms of the observed activation thermodynamics.