A specific point mutant at position 1 of the influenza hemagglutinin fusion peptide displays a hemifusion phenotype.
A specific point mutant at position 1 of the influenza hemagglutinin fusion peptide displays a hemifusion phenotype.
复制标题
流感血凝素融合肽位置 1 的特定点突变表现出半融合表型。
DOI：
10.1091/mbc.10.8.2759
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发表时间：
1999
影响因子：
3.3
通讯作者：
White,JM
中科院分区：
文献类型：
--
作者：
Qiao,H;Armstrong,RT;Melikyan,GB;Cohen,FS;White,JM
我们之前表明，用 Glu 取代流感血凝素 (HA) 融合肽 Gly1 的第一个残基会消除融合活性。在本研究中，我们询问这种引人注目的表型是否是由于取代的谷氨酸的电荷或侧链体积所致。为此，我们生成并表征了 6 个在位置 1 进行取代的突变体：Gly1 替换为 Ala、Ser、Val、Glu、Gln 或 Lys。我们发现了以下内容。所有突变体均在细胞表面表达，可以从前体 (HA0) 裂解为允许融合的形式 (HA1-S-S-HA2)，结合针对主要抗原位点的抗体，结合红细胞，并在低 pH 下改变构象。在与红细胞融合过程中，只有甘氨酸、丙氨酸和丝氨酸支持脂质混合。只有 Gly 和 Ala 支持内容混合。因此，Ser HA 显示出半融合表型。 Ser HA 的半融合表型通过电生理学研究得到证实。我们的研究结果表明，HA 融合肽的第一个残基必须很小（例如，Gly、Ala 或 Ser），以促进脂质混合，并且必须很小且非极性（例如，Gly 或 Ala），以支持脂质和内容物混合。 Val HA 不表现出融合活性的发现强调了疏水性并不是决定融合肽功能的唯一因素的观点。 Ser HA 显示半融合这一令人惊讶的发现表明，HA 胞外域不仅在融合的第一阶段（脂质混合）中发挥作用，而且直接或间接地在融合的第二阶段（内容物混合）中发挥作用。
We showed previously that substitution of the first residue of the influenza hemagglutinin (HA) fusion peptide Gly1 with Glu abolishes fusion activity. In the present study we asked whether this striking phenotype was due to the charge or side-chain volume of the substituted Glu. To do this we generated and characterized six mutants with substitutions at position 1: Gly1 to Ala, Ser, Val, Glu, Gln, or Lys. We found the following. All mutants were expressed at the cell surface, could be cleaved from the precursor (HA0) to the fusion permissive form (HA1-S-S-HA2), bound antibodies against the major antigenic site, bound red blood cells, and changed conformation at low pH. Only Gly, Ala, and Ser supported lipid mixing during fusion with red blood cells. Only Gly and Ala supported content mixing. Ser HA, therefore, displayed a hemifusion phenotype. The hemifusion phenotype of Ser HA was confirmed by electrophysiological studies. Our findings indicate that the first residue of the HA fusion peptide must be small (e.g., Gly, Ala, or Ser) to promote lipid mixing and must be small and apolar (e.g., Gly or Ala) to support both lipid and content mixing. The finding that Val HA displays no fusion activity underscores the idea that hydrophobicity is not the sole factor dictating fusion peptide function. The surprising finding that Ser HA displays hemifusion suggests that the HA ectodomain functions not only in the first stage of fusion, lipid mixing, but also, either directly or indirectly, in the second stage of fusion, content mixing.