Characterization of a 120-Kilodalton pre-S-binding protein as a candidate duck hepatitis B virus receptor.
Infection by human and animal hepadnaviruses displays remarkable host and tissue tropism. The infection cycle probably initiates with binding of the pre-S domain of viral envelope protein to surface receptors present on the hepatocyte. Three types of neutralizing monoclonal antibodies against duck hepatitis B virus (DHBV) have their binding sites clustered within residues 83 to 107 of the pre-S protein, suggesting that this region may constitute a major receptor binding site. A 170- or 180-kDa duck protein (p170 or gp180) which binds DHBV particles through this part of the pre-S sequence has been identified recently. Although the p170 binding protein is host (duck) specific, its distribution is not restricted to DHBV-infectible tissues. Using the pre-S protein fused to glutathione S-transferase and immobilized on Sepharose beads, we have now identified an additional binding protein with a size of 120 kDa (p120). p120 expression is restricted to the liver, kidney, and pancreas, the three major organs of DHBV replication. While optimal p170 binding requires an intact pre-S protein, binding to p120 occurs much more efficiently with a few N- or C-terminally truncated forms. The p120 binding site was mapped to residues 98 to 102 of the pre-S region, which overlaps with a cluster of known virus-neutralizing epitopes. Site-directed mutagenesis revealed residues 100 to 102 (Phe-Arg-Arg) as the critical p120 contact site; nonconservative substitution in any of the three positions abolished p120 binding. Double mutations at positions 100 to 102 markedly reduced DHBV infectivity in cell culture. Short pre-S peptides covering the clustered neutralizing epitopes (also p170 and p120 binding sites) reduced DHBV infectivity in primary duck hepatocyte cultures. Thus, p120 represents a candidate component of the DHBV receptor complex.
Li
J S
JS
Molecular Hepatology Laboratory, Massachusetts General Hospital Cancer Center, Charlestown, Massachusetts 02129, USA.
Tong
S P
SP
Wands
J R
JR
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D004372:Ducks; D000939:Epitopes / Q000032:analysis; D015686:Gene Products, env / Q000737:chemistry / Q000378:metabolism*; D015611:Hepatitis B Virus, Duck / Q000502:physiology*; D006801:Humans; D007668:Kidney / Q000821:virology; D008099:Liver / Q000821:virology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D009928:Organ Specificity; D010179:Pancreas / Q000821:virology; D016133:Polymerase Chain Reaction; D011991:Receptors, Virus / Q000302:isolation & purification / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014779:Virus Replication
D000939:Epitopes; D015686:Gene Products, env; D011991:Receptors, Virus; D011993:Recombinant Fusion Proteins