Study of hemagglutinin membrane fusion domain

流感病毒糖蛋白血凝素（HA） HA2结构域的23个n端残基中，除5个外，在所有16种血清型HA基因中都是严格保守的。这种HA2融合肽（HAfp）的结构和功能一直是广泛的生物物理、计算和功能分析的焦点，但大多数这些分析都是不包括严格保守残基Trp21-Tyr22-Gly23的肽。我们对溶解在十二烷基磷脂酰胆碱（DPC）中的血清型H1亚型的全长HAfp进行了异核三重共振NMR研究，发现其具有非常紧密的螺旋发夹结构，其n端α -螺旋（Gly1-Glu11）与第二α -螺旋（Trp14-Gly23）紧密排列，7个保守残基中有6个位于螺旋界面。位于第13位的第七个保守残基采用正的phi角，使得连接两个螺旋的发夹旋转成为可能。该结构由多个螺旋间的CaH - C=O氢键稳定，具有强螺旋间的HN-H&#61537；和H&#61537；-H&#61537； NOE触点。15N弛豫分析表明该结构在纳秒级时间尺度上高度有序，NOE分析表明HAfp位于水-脂质界面，疏水表面面向脂质环境，螺旋-螺旋界面富gly侧暴露于溶剂。为了提高分辨率，我们在两种不同的对准介质（聚丙烯酰胺凝胶和液晶DNA）中记录了N-H和Ca-Ha相互作用的大量残余偶极耦合测量。从融合域的单体形式的新数据中得出的结构与早期的研究相比有许多相似之处，但也有明显的差异。

All but five of the N-terminal 23 residues of the HA2 domain of the influenza virus glycoprotein hemagglutinin (HA) are strictly conserved across all 16 serotypes of HA genes. The structure and function of this HA2 fusion peptide (HAfp) continues to be the focus of extensive biophysical, computational, and functional analysis, but most of these analyses are of peptides that do not include the strictly conserved residues Trp21-Tyr22-Gly23. Our heteronuclear triple resonance NMR study of full length HAfp of sero subtype H1, solubilized in dodecylphosphatidyl choline (DPC), reveals a remarkably tight helical hairpin structure, with its N-terminal alpha-helix (Gly1-Glu11) packed tightly against its second alpha-helix (Trp14-Gly23), with six of the seven conserved Gly residues at the interhelical interface. The seventh conserved Gly residue in position 13 adopts a positive phi angle, enabling the hairpin turn that links the two helices. The structure is stabilized by multiple interhelical CaH to C=O hydrogen bonds, characterized by strong interhelical HN-H and H-H NOE contacts. 15N relaxation analysis indicates the structure to be highly ordered on the nanosecond time scale, and NOE analysis indicates HAfp is located at the water-lipid interface, with its hydrophobic surface facing the lipid environment, and the Gly-rich side of the helix-helix interface exposed to solvent.To enhance the resolution, we have recorded extensive residual dipolar coupling measurements in two different alignment media (polyacrylamide gel and liquid crystalline DNA) for both N-H and Ca-Ha interactions. Structures derived from the new data for the monomeric form of the fusion domain show many similarities but also distinct differences relative to those of earlier studies.