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首页> 外文期刊>Journal of Molecular Biology >pH-dependent self-association of influenza hemagglutinin fusion peptides in lipid bilayers
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pH-dependent self-association of influenza hemagglutinin fusion peptides in lipid bilayers

机译：脂质双层中流感血凝素融合肽的pH依赖性自缔合

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摘要

We have recently designed a host-guest peptide system that allows us to quantitatively measure the energetics of interaction of viral fusion peptides with lipid bilayers. Here, we show that fusion peptides of influenza hemagglutinin reversibly associate with one another at membrane surfaces above critical surface concentrations, which range from one to five peptides per 1000 lipids in the systems that we investigated. It is further demonstrated by using circular dichroism and Fourier transform infrared spectroscopy that monomeric peptides insert into the bilayers in a predominantly alpha -helical conformation, whereas self-associated fusion peptides adopt predominantly antiparallel beta -sheet structures at the membrane surface. The two forms are readily interconvertible and the equilibrium between them is determined by the pH and ionic strength of the surrounding solution. Lowering the pH favors the monomeric alpha -helical conformation, whereas increasing the ionic strength shifts the equilibrium towards the membrane-associated beta -aggregates. The binding data are interpreted in terms of a cooperative binding model that yields free energies of insertion and free energies of self-association for each of the peptides studied at pH 7.4 and pH 5. At pH 5 and 35 mM ionic strength, the insertion energy of the 20 residue influenza hemagglutinin fusion peptide is -7.2 kcal/mol and the self-association energy is -1.9 kcal/mol. We propose that self-association of fusion peptides could be a major driving force for recruiting a small number of hemagglutinin trimers into a fusion site. (C) 2000 Academic Press. [References: 43]
机译：我们最近设计了一种宿主-客体肽系统，该系统可以定量测量病毒融合肽与脂质双层相互作用的能量。在这里，我们显示流感血凝素的融合肽在高于临界表面浓度的膜表面相互可逆地缔合，在我们研究的系统中，这种浓度范围为每1000个脂质1至5个肽。通过使用圆二色性和傅立叶变换红外光谱进一步证明，单体肽以主要α-螺旋构象插入双层中，而自缔合融合肽在膜表面主要采用反平行β-折叠结构。两种形式易于互换，它们之间的平衡取决于周围溶液的pH值和离子强度。降低pH有利于单体α-螺旋构象，而增加离子强度则使平衡向膜相关的β-聚集体转移。结合数据是根据协同结合模型来解释的，该模型产生了在pH 7.4和pH 5下研究的每种肽的插入自由能和自缔合自由能。在pH 5和35 mM离子强度下，插入能20个残基的流感血凝素融合肽的Aβ为-7.2kcal / mol，自缔合能为-1.9kcal / mol。我们提出融合肽的自缔合可能是招募少量血凝素三聚体进入融合位点的主要驱动力。 （C）2000学术出版社。 [参考：43]

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