Lin Y, Liu Y X, Cislo T, Mason B L, Yu M Y
Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892.
J Med Virol. 1991 Mar;33(3):181-7. doi: 10.1002/jmv.1890330308.
The infectious particles of hepatitis B virus (HBV) contain 3 related surface antigens, i.e., small, medium, and large, all of which are encoded by one large open reading frame with multiple initiation codons. The large surface antigen (L-Ag) contains preS1, preS2, and S regions while both the middle and small surface antigens lack preS1. Several lines of evidence suggested that the preS1 region is involved in the binding of HBV to human hepatocytes as shown by its binding to HepG2 cells and isolated human hepatocyte membranes. To obtain large quantity of preS1 peptide, an expression vector was constructed containing a lac promoter, the 5' half of the beta-galactosidase gene, the Factor Xa tetrapeptide recognition sequence, and the coding region of preS1 plus preS2. This recombinant plasmid constitutively produced high concentration of a fusion protein in inclusion bodies in Escherichia coli. When the fusion protein was treated with Factor Xa, a peptide consisting of the N-terminal 91 amino acids of the preS1 region was released. This preS1 fragment purified by anion exchange chromatography was able to bind specifically to the isolated plasma membranes from human liver. Hence, this recombinant preS1 peptide can be used to identify and isolate hepatocyte receptors for HBV.
乙型肝炎病毒（HBV）的感染性颗粒含有3种相关的表面抗原，即小分子、中分子和大分子，它们均由一个带有多个起始密码子的大开放阅读框编码。大表面抗原（L-Ag）包含前S1、前S2和S区，而中分子和小分子表面抗原均缺乏前S1。多项证据表明，前S1区参与HBV与人肝细胞的结合，这一点已通过其与HepG2细胞和分离的人肝细胞膜的结合得到证实。为了获得大量的前S1肽，构建了一个表达载体，该载体包含一个乳糖启动子、β-半乳糖苷酶基因的5' 端、因子Xa四肽识别序列以及前S1加前S2的编码区。这种重组质粒在大肠杆菌的包涵体中持续产生高浓度的融合蛋白。当用因子Xa处理融合蛋白时，会释放出一个由前S1区N端91个氨基酸组成的肽。通过阴离子交换色谱法纯化的该前S1片段能够特异性结合从人肝脏分离的质膜。因此，这种重组前S1肽可用于鉴定和分离HBV的肝细胞受体。
