Turner Peter C, Moyer Richard W
Department of Molecular Genetics and Microbiology, Box 100266/1600 SW Archer Road, ARB R2-231, University of Florida, Gainesville, FL 32610-0266, USA.
Virology. 2006 Mar 30;347(1):88-99. doi: 10.1016/j.virol.2005.11.012. Epub 2005 Dec 27.
The serpin SPI-3 and the hemagglutinin (HA) encoded by cowpox virus (CPV) block cell-cell fusion, and colocalize at the cell surface. wtCPV does not fuse cells, but inactivation of either gene leads to fusion. SPI-3 mAb added to wtCPV-infected cells caused fusion, confirming that SPI-3 protein at the cell surface prevents fusion. The SPI-3 mAb epitope mapped to an 85-amino acid region at the C-terminus. Removal of either 44 residues from the SPI-3 C-terminus or 48 residues following the N-terminal signal sequence resulted in fusion. Interaction between SPI-3 and HA proteins in infected cells was shown by coimmunoprecipitation. SPI-3/HA was not associated with the A27L "fusion" protein. SPI-3 and HA were able to associate in uninfected cells in the absence of other viral proteins. The HA-binding domain in SPI-3 resided in the C-terminal 229 residues, and did not include helix D, which mediates cofactor interaction in many other serpins.
丝氨酸蛋白酶抑制剂SPI-3和牛痘病毒（CPV）编码的血凝素（HA）可阻止细胞间融合，并共定位于细胞表面。野生型CPV不会使细胞融合，但任一基因失活都会导致细胞融合。添加到野生型CPV感染细胞中的SPI-3单克隆抗体可引起细胞融合，证实细胞表面的SPI-3蛋白可阻止细胞融合。SPI-3单克隆抗体表位定位于C末端的一个85个氨基酸的区域。从SPI-3 C末端去除44个残基或从N末端信号序列之后去除48个残基都会导致细胞融合。共免疫沉淀显示了感染细胞中SPI-3和HA蛋白之间的相互作用。SPI-3/HA与A27L“融合”蛋白无关。在没有其他病毒蛋白的情况下，SPI-3和HA能够在未感染的细胞中结合。SPI-3中的HA结合结构域位于C末端的229个残基中，不包括在许多其他丝氨酸蛋白酶抑制剂中介导辅因子相互作用的螺旋D。
