Lee Changhee, Yoo Dongwan
Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
J Gen Virol. 2005 Nov;86(Pt 11):3091-3096. doi: 10.1099/vir.0.81160-0.
Porcine reproductive and respiratory syndrome virus (PRRSV) open reading frame (ORF) 2a contains a small internal ORF (2b) capable of encoding a protein of 73 aa, termed E protein. The function of E protein is currently unknown. The E protein possesses two cysteines at positions 49 and 54 that are highly conserved among North American isolates. In the present study, it was shown that E protein did not homodimerize with itself nor did it heterodimerize with the nucleocapsid (N) protein. However, E protein was interactive non-covalently with itself or with the N protein as shown by pull-down assays. The significance of the E protein cysteine residues on virus replication was determined using an infectious clone. Each cysteine was substituted by serine and the mutations were introduced into a full-length clone of PRRSV. When transfected into Marc-145 cells, all cysteine mutant clones induced PRRSV-specific cytopathic effects and produced infectious progeny virus. The data indicate that cysteine residues in the E protein are not essential for replication of North American genotype PRRSV.
猪繁殖与呼吸综合征病毒（PRRSV）开放阅读框（ORF）2a包含一个小的内部开放阅读框（2b），能够编码一种73个氨基酸的蛋白质，称为E蛋白。E蛋白的功能目前尚不清楚。E蛋白在第49和54位具有两个半胱氨酸，在北美分离株中高度保守。在本研究中，结果表明E蛋白既不与自身形成同源二聚体，也不与核衣壳（N）蛋白形成异源二聚体。然而，如下拉实验所示，E蛋白与自身或与N蛋白存在非共价相互作用。使用感染性克隆确定了E蛋白半胱氨酸残基对病毒复制的意义。每个半胱氨酸被丝氨酸取代，并将突变引入PRRSV的全长克隆中。当转染到Marc-145细胞中时，所有半胱氨酸突变克隆均诱导出PRRSV特异性细胞病变效应并产生感染性子代病毒。数据表明，E蛋白中的半胱氨酸残基对于北美基因型PRRSV的复制不是必需的。
