Wootton Sarah K, Rowland Raymond R R, Yoo Dongwan
Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
J Virol. 2002 Oct;76(20):10569-76. doi: 10.1128/jvi.76.20.10569-10576.2002.
Porcine reproductive and respiratory syndrome virus (PRRSV) is a cytoplasmic RNA virus with the unique or unusual feature of having a nucleocapsid (N) protein that is specifically transported to the nucleolus of virus-infected cells. In this communication, we show that the N protein is a phosphoprotein. Phosphoamino acid analysis of authentic and recombinant N proteins demonstrated that serine residues were exclusively phosphorylated. The pattern of phosphorylated N protein cellular distribution in comparison with that of [(35)S]methionine-labeled N protein suggested that phosphorylation does not influence subcellular localization of the protein. Time course studies showed that phosphorylation occurred during, or shortly after, synthesis of the N protein and that the protein remained stably phosphorylated throughout the life cycle of the virus to the extent that phosphorylated N protein was found in the mature virion. Two-dimensional electrophoresis and acid-urea gel electrophoresis showed that one species of the N protein is predominant in virus-infected cells, suggesting that multiple phosphorylated isoforms of N do not exist.
猪繁殖与呼吸综合征病毒（PRRSV）是一种细胞质RNA病毒，具有独特或不寻常的特征，即其核衣壳（N）蛋白会特异性转运至病毒感染细胞的核仁。在本通讯中，我们表明N蛋白是一种磷蛋白。对天然和重组N蛋白的磷酸氨基酸分析表明，只有丝氨酸残基被磷酸化。与[³⁵S]甲硫氨酸标记的N蛋白相比，磷酸化N蛋白的细胞分布模式表明磷酸化并不影响该蛋白的亚细胞定位。时间进程研究表明，磷酸化发生在N蛋白合成期间或之后不久，并且在病毒的整个生命周期中该蛋白都保持稳定的磷酸化状态，以至于在成熟病毒粒子中也能发现磷酸化的N蛋白。二维电泳和酸性尿素凝胶电泳表明，在病毒感染细胞中一种N蛋白占主导，这表明不存在N蛋白的多种磷酸化异构体。
