Protein kinase R plays a key role in innate antiviral immune responses of vertebrate animals. Most mammalian poxviruses encode two PKR antagonists, E3 (dsRNA binding) and K3 (eIF2α homolog) proteins. In this study, the role of K3 family proteins from poxviruses with distinct host tropisms in determining the virus host range was examined in a vaccinia E3L deletion mutant virus. It was found that K3 orthologs from the species-specific poxviruses (taterapox virus, sheeppox virus, myxoma virus, swinepox virus and yaba monkey tumor virus) restored the virus replication competency in cells derived from their natural hosts or related animal species. Further, it was found that the residues located in the helix insert region of the protein, K45 of vaccinia K3 and Y47 of the sheep poxvirus ortholog 011, are critical for the virus host species specificity. These observations demonstrate that poxvirus K3 proteins are major determinants of the virus host specificity.

中文翻译：

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痘病毒编码的eIF2α同源物K3家族蛋白是痘病毒宿主物种特异性的关键决定因素。

蛋白激酶R在脊椎动物的先天抗病毒免疫应答中起关键作用。大多数哺乳动物痘病毒编码两种PKR拮抗剂：E3（与dsRNA结合）和K3（与eIF2α同源）蛋白。在这项研究中，检查了痘苗病毒E3L缺失突变病毒中来自宿主嗜性不同的痘病毒K3家族蛋白在确定病毒宿主范围中的作用。已发现，来自物种特异性痘病毒（塔特拉波克斯病毒，羊痘病毒，粘液瘤病毒，猪痘病毒和亚巴猴肿瘤病毒）的K3直系同源物在其天然宿主或相关动物物种衍生的细胞中恢复了病毒复制能力。此外，发现位于牛痘病毒K3的K45蛋白和羊痘病毒ortholog 011的Y47蛋白的螺旋插入区中的残基对于病毒宿主物种特异性至关重要。