Study of hemagglutinin membrane fusion domain

流感病毒糖蛋白血凝素（HA）的HA 2结构域的N-末端23个残基中除5个之外的所有残基在HA基因的所有16种血清型中是严格保守的。 这种HA 2融合肽（HAfp）的结构和功能仍然是广泛的生物物理、计算和功能分析的焦点，但这些分析中的大多数是不包括严格保守的残基Trp 21-Tyr 22-Gly 23的肽。 我们的异源三重共振NMR研究全长H1血清亚型HAfp，溶解在十二烷基磷脂酰胆碱（DPC），揭示了一个非常紧密的螺旋发夹结构，其N-末端α-螺旋（Gly 1-Glu 11）紧密包装对它的第二个α-螺旋（Trp 14-Gly 23），与六个保守的Gly残基在螺旋间的接口。 第七个保守的Gly残基在位置13采取一个积极的phi角，使发夹的转折，连接两个螺旋。 该结构通过多个螺旋间CaH至C=O氢键稳定，其特征在于强螺旋间HN-H和H-H NOE接触。 15 N弛豫分析表明其结构在纳秒时间尺度上是高度有序的，NOE分析表明HAfp位于水-脂界面，其疏水表面面向脂环境，螺旋-螺旋界面的富含Gly的一侧暴露于溶剂。我们在两种不同的取向介质（聚丙烯酰胺凝胶和液晶DNA）中记录了N-H和Ca-Ha相互作用的广泛的残余偶极耦合测量。 来自融合域的单体形式的新数据的结构显示出许多相似之处，但也有明显的差异，相对于那些早期的研究。

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.