Fang Q, Seng E K, Ding Q Q, Zhang L L
State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China.
Arch Virol. 2008;153(4):675-82. doi: 10.1007/s00705-008-0048-3. Epub 2008 Feb 14.
Proteolytic cleavages play an important role in reovirus infection during entry into cells. The effects of protease digestion on the morphology, infectivity and polypeptide composition of grass carp reovirus (GCRV) were investigated. Following treatment with chymotrypsin, the different subviral particles of GCRV were isolated using density gradient centrifugation and examined by electron microscope (EM). Analysis of protein components revealed that the viral outer capsid was composed of VP5 and VP7. Of particular note, VP5 was found to primarily exist within virions as cleaved fragments, which was consistent with observations for its analogue mu1/mu1C, generated by autolysis of mu1 at the mu1N/mu1C junction for mammalian orthoreoviruses (MRVs). Meanwhile, both trypsin- and chymotrypsin-treated GCRV particles appeared to have an enhanced infectivity. Moreover, the corresponding assays between infectivity and protein component indicated that the enhancement of infectivity was correlated to the complete digestion of the outer capsid protein VP7 and partial cleavage of VP5. Overall, the results presented in this paper provided strong evidence that the proteins VP5 and VP7 of GCRV play an indispensable role in viral infection.
蛋白水解切割在呼肠孤病毒进入细胞的感染过程中发挥着重要作用。研究了蛋白酶消化对草鱼呼肠孤病毒（GCRV）的形态、感染性和多肽组成的影响。用胰凝乳蛋白酶处理后，通过密度梯度离心分离GCRV的不同亚病毒颗粒，并用电镜（EM）进行检查。蛋白质成分分析表明，病毒外衣壳由VP5和VP7组成。特别值得注意的是，发现VP5主要以切割片段的形式存在于病毒粒子中，这与哺乳动物正呼肠孤病毒（MRV）中由mu1在mu1N/mu1C连接处自溶产生的类似物mu1/mu1C的观察结果一致。同时，经胰蛋白酶和胰凝乳蛋白酶处理的GCRV颗粒似乎都具有增强的感染性。此外，感染性与蛋白质成分之间的相应测定表明，感染性的增强与外衣壳蛋白VP7的完全消化和VP5的部分切割有关。总体而言，本文给出的结果提供了有力证据，证明GCRV的蛋白VP5和VP7在病毒感染中起着不可或缺的作用。
