[Effects of disulfide bridges in glycoprotein E1 on the membrane fusion activity of rubella virus].

To reveal the effects of disulfide bridges in rubella virus glycoprotein E1 on the membrane fusion activity, the recombinant plasmid pBSK-SPE2E1 and site-directed mutagenesis to mutate 11 cysteines individually in the ectodomain of E1 to remove a disulfide bridge from the wild-type E1 were constructed. All mutants and the wild-type plasmid were expressed on BHK-21 cell. Giemsa Staining was used to show the polykaryon formed in the transfected BHK-21 cells. The cell surface expression efficiency of the plasmids was assayed with fluorescence-activated cell sorter (FACS). Hemadsorption was performed to detect the receptor recognition activity of the recombinant plasmids. The results showed that all the 10 disulfide bridges in the ectodomain of E1 played an important role in the process of the membrane fusion. The removal of any disulfide bridge resulted in the loss of the fusion activity. The disulfide formed by the 5th and the 8th cysteine might be critical for the interaction of E1 and E2. While the disulfide bridges formed by the 3rd, the 4th, and the 13th might influence the membrane fusion activity of E1 directly.