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Hepatitis B viral infection, like other viruses, it should first bind to the r
eceptor(s) on the target cell surface by its envelope protein and the membrane
fusion will occur between HBV and target cell. After entering the cell, it wi
ll begin its replication. So successful infection of HBV depends on whether HB
V could bind the receptor(s) on the target cell. It is not yet clear what is H
BV receptor. There are data showing that the HBV large surface antigen (L) is
involved in the viral-cell interaction. The pre-S1 region of L binds to the re
ceptor(s) and the amino acid residues to 47 in the pre-S1 region may be the s
pecific binding site. The pre-S2 may help and increase the binding efficiency.
We tried to find the HBV receptor(s) by the RAP in situ method. Two kinds of p
re-S1-alkaline phosphatase (AP) fusion proteins, N-terminal insertion and C-te
rminal insertion were constructed. These two fusion proteins had different mol
ecular weight and different biological functions. As experiments found, the di
fference in molecule weight was partially due to the glycosylation pattern bet
ween these fusion proteins. Both the constructs could bind to the hepatocytes
on the frozen liver tissue section but with different efficiency. The binding
could be partially blocked by the pre-S1, suggesting that this binding is spec
ific. Further modification will make the fusion proteins as useful probes in t
he searching for HBV receptor(s).By fusing the putative receptor binding domai
n (pre-S1) of HBV envelope protein to the reporter molecular (in this case is
human placenta alkaline phosphatase), we could use the chimera proteins to ide
ntify its cellular binding counterparts (may be receptors).
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