Zheng D X, Dickens L, Liu T Y, Nakhasi H L
Division of Biochemistry and Biophysics, Food and Drug Administration, Bethesda, MD 20892.
Gene. 1989 Oct 30;82(2):343-9. doi: 10.1016/0378-1119(89)90061-9.
A full-length cDNA clone for the 24S subgenomic mRNA of the vaccine strain (HPV77) of rubella virus has been isolated from a cDNA library made from the RNAs of infected cells. Starting from the first Met start codon, the 24S mRNA codes for a precursor protein of 1063 amino acids (aa). This precursor encodes a capsid protein of 300 aa, and two envelope proteins, E1 (481 aa) and E2 (282 aa). Both the E1 and E2 proteins are preceded by a stretch of 21 hydrophobic aa, characteristic of a signal peptide, and each has three putative glycosylation sites in the polypeptide chains. Comparison between the structural proteins of the vaccine and the wild-type (wt; M33) strains of rubella virus, revealed that the E2 protein of the vaccine strain differs, in its apparent Mr, by approx. 3 kDa, from the wt strain. The difference could be due to decreased glycosylation of the vaccine strain E2 protein, as revealed by [3H]mannose incorporation studies. Five single-aa changes in the structural proteins occurred during the attenuation process, one each in the capsid and the E1 protein and three in the E2 protein. The change of Thr-412----Ile in the E2 protein results in the loss of a putative glycosylation site at Asn-410, which offers a plausible explanation for decreased glycosylation of the E2 protein from the vaccine strain of rubella virus.
已从感染细胞RNA构建的cDNA文库中分离出风疹病毒疫苗株（HPV77）24S亚基因组mRNA的全长cDNA克隆。从第一个Met起始密码子开始，24S mRNA编码一个含1063个氨基酸（aa）的前体蛋白。该前体编码一个含300个aa的衣壳蛋白以及两个包膜蛋白E1（481个aa）和E2（282个aa）。E1和E2蛋白之前均有一段21个疏水aa的序列，这是信号肽的特征，并且每个在多肽链中都有三个推定的糖基化位点。风疹病毒疫苗株和野生型（wt；M33）株的结构蛋白比较显示，疫苗株的E2蛋白在表观Mr上与wt株相差约3 kDa。如[3H]甘露糖掺入研究所示，这种差异可能是由于疫苗株E2蛋白糖基化减少所致。在减毒过程中，结构蛋白发生了五个单氨基酸变化，衣壳蛋白和E1蛋白各有一个，E2蛋白有三个。E2蛋白中Thr-412----Ile的变化导致Asn-410处一个推定糖基化位点的丧失，这为风疹病毒疫苗株E2蛋白糖基化减少提供了一个合理的解释。
