Copyright © 1991, American Society for Microbiology Differential Formation of Disulfide Linkages in the Core Antigen of Extracellular and Intracellular

Our understanding of the assembly of hepatitis B virus is still very limited. We present evidence to demonstrate that the HBc antigen formed oligomers through disulfide linkages in the extracellular hepatitis B virus core (HBc) particles. However, the intracellular HBV core particles did not contain disulfide-linked HBc antigens. Furthermore, the extracellular particles which had disulfide bonds were more stable than intracel-lular particles at pH 7.5 and 10 and in 3 M NaCl and 4 M urea. These data suggest that the formation of disulfide bonds in the HBc antigen is important for the integrity of the viral core particles. The nucleocapsid core of hepatitis B virus (HBV) is composed of the core (HBc) antigen (2), the viral genome (24), a 5'-end-binding protein (11), a polymerase (15), and a core particle-associated protein kinase (1). Very little is known about the assembly of these components during the formation of the nucleocapsid core of HBV. Apparently, the HBc antigen is the major structural constituent of the nucleocapsid core (12). The C terminus of the HBc antigen is extremely rich in arginine, serine, and proline residues