The proteins of hepatitis B dane particle cores

Abstract

Although several studies have been done to analyze the peptides of purified 22-nm Hb_sAg particles, no information has been published about the peptides of the core of the Dane particle which bears the other hepatitis B viral antigen, Hb_cAg. Dane particles and Dane particle cores (produced by NP-40 treatment of Dane particles) were purified by equilibrium centrifugation in CsCl density gradients. Two populations of Dane particles were observed at densities 1.27 and 1.24 g/ml, respectively. The higher buoyant density Dane particles yielded exclusively cores of buoyant density 1.38 g/ml in CsCl, and the lower buoyant density Dane particles yielded two kinds of cores with buoyant densities of 1.38 and 1.325 g/ml, respectively. Only the higher density Dane particles and cores manifested endogenously primed DNA polymerase activity. The peptides of density 1.38 g/ml Dane particle cores purified by equilibrium CsCl density gradient centrifugation and HB_cAg particles from HBV infected chimpanzee liver purified in the same way were analyzed by SDS-polyacrylamide gel electrophoresis. Both kinds of particles were found to consistently contain 3 Coomassie blue staining peptides with approximate molecular weights of 19,000, 70,000 and 80,000 daltons (designated P-19, P-70 and P-80 respectively). In addition, the HB_cAg particles from infected liver regularly yielded a protein component with molecular weight greater than 200,000 daltons. This component was occasionally present in electrophoresis runs of core peptides from only one of two patients. Its irregular appearance after gel electrophoresis suggests it may have been an aggregate not completely dissociated under the conditions used. The lower density core component consistently contained P-19, P-70, and P-80, and infrequently additional minor peptides of uncertain origin. The irregular occurrence of the minor peptides in varying amounts suggests they were not intrinsic core proteins.