Crystallization of hepatitis B virus core protein shells: determination of cryoprotectant conditions and preliminary X-ray characterization

Hepatitis B virus causes liver cirrhosis and hepatocellular cancer and is a major cause of death, particularly in Asia and sub-Saharan Africa. The virus consists of an inner core or nucleocapsid, which encloses the viral nucleic acid, with an outer lipid envelope containing surface-antigen proteins. The core protein, when expressed in E. coli, assembles into spherical shells containing 180 or 240 subunits, arranged with T = 3 or T = 4 icosahedral symmetry. The C-terminal region of the protein is involved in nucleic acid binding, and deletion of this region does not prevent capsid formation. C-terminally deleted hepatitis B core shells containing 240 subunits have been crystallized and data has been collected to 3.6 Å resolution from frozen crystals, using butanediol as a cryoprotectant. The crystals have C2 symmetry, with unit-cell parameters a = 538.0, b = 353.0, c = 369.6 Å, β = 132.3°.