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Interaction between hepatitis B surface proteins and monomeric human serum albumin
B Krone1, A Lenz, K H Heermann
1Department of Medical Microbiology, University of Göttingen, West Germany.
Hepatology (Baltimore, Md.)
|June 1, 1990
Summary
Natural human serum albumin binds to hepatitis B surface antigen (HBsAg) via its preS2 domain. This binding can be reversible or irreversible, involving covalent bonds with small HBs proteins.
Area of Science:
- Hepatology
- Virology
- Biochemistry
Background:
- Hepatitis B surface antigen (HBsAg) is known to bind polymerized human serum albumin (HSA).
- The interaction between natural HSA and hepatitis B virus (HBV) under physiological conditions remains unclear.
Purpose of the Study:
- To investigate the binding of natural and recombinant HBsAg to monomeric HSA.
- To characterize the binding sites and mechanisms involved in HBsAg-HSA interactions.
Main Methods:
- Immunological, biochemical, and biophysical techniques were employed.
- HBsAg spheres were analyzed for HSA binding capacity.
- Binding sites were localized using domain-specific analysis (preS2 and S domains).
- Copurification studies and dissociation experiments (high-salt, disulfide cleavage, trypsin digestion) were performed.
Main Results:
- HBsAg spheres exhibited variable binding capacity for HSA (up to six HSA molecules/sphere).
- A reversible binding site for HSA was identified exclusively in the preS2 domain of HBsAg.
- HSA copurified with HBsAg and existed in monomeric form.
- HSA binding involved both reversible (preS2 domain) and irreversible (covalent linkage to small HBs proteins via cysteine residues) mechanisms.
Conclusions:
- Natural human serum albumin binds to HBsAg, primarily through the preS2 domain.
- Irreversible binding occurs via covalent bonds to cysteine residues in small HBs proteins.
- These findings elucidate novel interactions between HBsAg and human serum albumin.