Function and Structure of Carboxypeptidase gp180.

我们已经描述了一个180 kDa的宿主细胞糖蛋白（gp 180），结合DHBV颗粒。从gp 180 cDNA和基因组DNA的序列来看，gp 180由1389个氨基酸组成，实际上是三个羧肽酶同源结构域的首尾排列。gp180缺失突变体与鸭乙型肝炎病毒包膜蛋白（preS）的结合试验表明，preS结合在gp180的第三个羧肽酶结构域（C结构域）上。为了解鸭糖蛋白180在鸭乙型肝炎病毒（DHBV）进入途径中的作用，本研究将鸭糖蛋白180基因（gp180DNA）与neo基因共转染，建立了表达鸭糖蛋白190的细胞系。DHBV颗粒吸附在这些细胞上。但未检测到DHBV在细胞内的增殖。为了解gp180在DHBV进入途径中的作用及gp180在DHBV体内的分布，制备了抗gp180抗体。这些抗体不能阻断gp180与DHBV preS的结合。我们正在研制gp180的preS中和抗体。GP 180可以作为完整的形式。通过Western分析和Southern分析确定鸡gp180的存在。这一事实表明，gp180的独特结构不是鸭所特有的。gp 180可能广泛分布于脊椎动物中。

We have described a 180 kDa host cell glycoprotein (gp 180) that bound DHBV particles. From the sequence of gp 180 cDNAs and genomic DNA,gp 180 consists of 1389 amino acids and is actually a head-to-tail array of three carboxypeptidase homology domains. Less than 10% of total gp 180 were localized on the cell surface.The binding assay of gp 180 deletion mutants to DHBV envelope protein (preS) shows that preS binds on the third carboxypeptidase domain (domain C) of gp 180. The assay of carboxypeptidase activity of each domain is progressing.To know the function of gp 180 on the entry pathway of DHBV,the cell lines expressing duck gp 190 were established by the transfection of plasmid DNA habroring gp 180 DNA and neo gene. DHBV particles adsorped on these cells. But we could not detect the proliferation of DHBV in the cells. These results indicate that gp 180 may act on the early atage of DHBV infection.To know the function of gp 180 on the entry pathway of DHBV and the distribution of gp 180, anti-gp 180 antibodies were prepared from rabbits and mouse. These antibodies could not block the binding of gp 180 to DHBV preS.We are progressing to make the neutralizing antibodies of gp 180 to preS.We could not detect processed products of gp 180 by the western analysis using anti-gp 180 antibodies. gp 180 may act as an intact from. The presence of chicken gp 180 was determined by the western analysis and by the southen analysis. This fact suggests that unique structure of gp 180 is not specific to duck. gp 180 may widely distribute in vertebrates.