Function and Structure of Carboxypeptidase gp180.

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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.