Electron microscopy of antibody complexes of influenza virus haemagglutinin in the fusion pH conformation.
Electron microscopy of antibody complexes of influenza virus haemagglutinin in the fusion pH conformation.
复制标题
电子显微镜观察融合 pH 构象的流感病毒血凝素抗体复合物。
作者：
S. Wharton;L. Calder;R. Ruigrok;J. Skehel;D. Steinhauer;D. Wiley
流感血凝素（HA）在内体pH下的膜融合潜力的激活需要其结构的改变。TBHA 2是HA的蛋白水解片段，在融合pH构象中，其X射线分析表明，在融合pH下，“融合肽”从其天然结构中的位置到11 nm三链卷曲螺旋的末端被置换> 10 nm，并且该结构的形成涉及HA的广泛再折叠或重组。在这里，我们用电子显微镜检查了TBHA 2的结构，并将其与病毒体中HA 2的融合pH结构、由可溶性菠萝蛋白酶释放的胞外域BHA在融合pH下形成的聚集体中的HA 2以及BHA在融合pH下结合的脂质体中的HA 2进行了比较。我们使用位点特异性单克隆抗体对每种HA 2制备物进行了定位以进行比较。我们得出结论，在融合的pH下，膜锚定和可溶性HA制剂的结构变化似乎是相同的;在不存在靶膜的情况下，病毒体中HA的“融合肽”与病毒体膜结合，使得HA 2在N末端和C末端都与膜结合，这意味着可以发生重新折叠的HA的反转;并且通过X射线分析观察到的结构变化不是由制备TBHA 2中使用的蛋白水解双链淀粉引起的。
Activation of the membrane fusion potential of influenza haemagglutinin (HA) at endosomal pH requires changes in its structure. X‐ray analysis of TBHA2, a proteolytic fragment of HA in the fusion pH conformation, indicates that at the pH of fusion the ‘fusion peptide’ is displaced by > 10 nm from its location in the native structure to the tip of an 11 nm triple‐stranded coiled coil, and that the formation of this structure involves extensive re‐folding or reorganization of HA. Here we examine the structure of TBHA2 with the electron microscope and compare it with the fusion pH structure of HA2 in virosomes, HA2 in aggregates formed at fusion pH by the soluble, bromelain‐released ectodomain BHA and HA2 in liposomes with which BHA associates at fusion pH. We have oriented each HA2 preparation for comparison, using site‐specific monoclonal antibodies. We conclude that the structural changes in membrane‐anchored and soluble HA preparations at the pH of fusion appear to be the same; that in the absence of a target membrane, the ‘fusion peptide’ of HA in virosomes associates with the virosome membrane so that HA2 is membrane bound at both N‐ and C‐termini, which implies that inversion of the re‐folded HA can occur; and that the structural changes observed by X‐ray analysis do not result from the proteolytic digestions used in the preparation of TBHA2.