van Staden V, Smit C C, Stoltz M A, Maree F F, Huismans H
Department of Genetics, University of Pretoria, South Africa.
Arch Virol Suppl. 1998;14:251-8. doi: 10.1007/978-3-7091-6823-3_22.
Each of the ten segments of the African horse sickness virus (AHSV) genome encodes at least one viral polypeptide. This report focuses on the nonstructural proteins NS1 and NS3, which are encoded by genome segments 5 and 10 respectively. The NS1 protein assembles into tubular structures, which are characteristically produced during orbivirus replication in infected cells. NS1 expressed by a recombinant baculovirus in Sf9 cells also forms tubules, which were analysed electron microscopically. These tubules had an average diameter of 23 +/- 2 nm, which is less than half the width of the corresponding bluetongue virus (BTV) tubules. They were also more fragile at high salt concentrations or pH. The cytotoxic effects produced by NS3 were examined by constructing of mutated versions and expressing them in insect cells. Substitution of amino acids 76-81 in a conserved region (highly conserved amongst all AHSV NS3 proteins, as well as other orbiviruses) with similar amino acids, did not influence the cytotoxicity of the mutant protein. However, mutation of four amino acids, from hydrophobic to charged amino residues, (aa 165-168) in a predicted transmembrane region of NS3, largely abolished its cytotoxic effect. It is considered likely that the mutant protein is unable to interact with cellular membrane components, thereby reducing its toxicity.
非洲马瘟病毒（AHSV）基因组的十个片段各自至少编码一种病毒多肽。本报告聚焦于非结构蛋白NS1和NS3，它们分别由基因组片段5和10编码。NS1蛋白组装成管状结构，这是在受感染细胞中环状病毒复制过程中典型产生的结构。由重组杆状病毒在Sf9细胞中表达的NS1也形成小管，并通过电子显微镜进行了分析。这些小管的平均直径为23±2纳米，不到相应蓝舌病毒（BTV）小管宽度的一半。它们在高盐浓度或pH条件下也更脆弱。通过构建突变体并在昆虫细胞中表达来检测NS3产生的细胞毒性作用。在保守区域（在所有AHSV NS3蛋白以及其他环状病毒中高度保守）用相似氨基酸替换76 - 81位氨基酸，不影响突变蛋白的细胞毒性。然而，在NS3预测的跨膜区域将四个氨基酸从疏水氨基酸突变为带电荷氨基酸（第165 - 168位氨基酸），很大程度上消除了其细胞毒性作用。据认为，突变蛋白可能无法与细胞膜成分相互作用，从而降低其毒性。
