Full Conversion of the Hemagglutinin-Neuraminidase Specificity of the Parainfluenza Virus 5 Fusion Protein by Replacement of 21 Amino Acids in Its Head Region with Those of the Simian Virus 41 Fusion Protein

For most parainfluenza viruses, a virus type-specific interaction between the hemagglutinin-neuraminidase (HN) and fusion (F) proteins is a prerequisite for mediating virus-cell fusion and cell-cell fusion. The molecular basis of this functional interaction is still obscure partly because it is unknown which region of the F protein is responsible for the physical interaction with the HN protein. Our previous cell-cell fusion assay using the chimeric F proteins of parainfluenza virus 5 (PIV5) and simian virus 41 (SV41) indicated that replacement of two domains in the head region of the PIV5 F protein with the SV41 F counterparts bestowed on the PIV5 F protein the ability to induce cell-cell fusion on coexpression with the SV41 HN protein while retaining its ability to induce fusion with the PIV5 HN protein. In the study presented here, we furthered the chimeric analysis of the F proteins of PIV5 and SV41, finding that the PIV5 F protein could be converted to an SV41 HN-specific chimeric F protein by replacing five domains in the head region with the SV41 F counterparts. The five SV41 F-protein-derived domains of this chimera were then divided into 16 segments; 9 out of 16 proved to be not involved in determining its specificity for the SV41 HN protein. Finally, mutational analyses of a chimeric F protein, which harbored seven SV41 F-protein-derived segments, revealed that replacement of at most 21 amino acids of the PIV5 F protein with the SV41 F-protein counterparts was enough to convert its HN protein specificity.

对于大多数副流感病毒而言，血凝素 - 神经氨酸酶（HN）蛋白和融合（F）蛋白之间的病毒类型特异性相互作用是介导病毒 - 细胞融合以及细胞 - 细胞融合的先决条件。这种功能性相互作用的分子基础仍然不清楚，部分原因是F蛋白中负责与HN蛋白发生物理相互作用的区域尚不明确。我们之前利用副流感病毒5（PIV5）和猴病毒41（SV41）的嵌合F蛋白进行的细胞 - 细胞融合试验表明，用SV41 F蛋白的相应部分替换PIV5 F蛋白头部区域的两个结构域，可使PIV5 F蛋白在与SV41 HN蛋白共表达时获得诱导细胞 - 细胞融合的能力，同时保留其与PIV5 HN蛋白诱导融合的能力。在此项研究中，我们进一步对PIV5和SV41的F蛋白进行了嵌合分析，发现通过用SV41 F蛋白的相应部分替换头部区域的五个结构域，可将PIV5 F蛋白转变为对SV41 HN蛋白特异性的嵌合F蛋白。然后将该嵌合体中来自SV41 F蛋白的五个结构域划分为16个片段；其中9个片段被证明与确定其对SV41 HN蛋白的特异性无关。最后，对一种包含7个来自SV41 F蛋白片段的嵌合F蛋白进行的突变分析表明，用SV41 F蛋白的相应部分替换PIV5 F蛋白最多21个氨基酸就足以改变其HN蛋白特异性。