Isolation and characterization of the major protein and glycoprotein of hepatitis B surface antigen

Abstract

Hepatitis B surface antigen has been purified and its major protein (p-25) and glycoprotein (gp-30) isolated. These isolated proteins have been subjected to amino acid analysis, Edman degradation (30 steps), carboxypeptidase digestion, and peptide mapping following tryptic hydrolysis by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, two-dimensional thin layer chromatography and electrophoresis, and high performance liquid chromatography. These studies demonstrated that p-25 and gp-30 have identical protein structure, differing only by the presence of carbohydrate in gp-30. Removal of this carbohydrate by treatment with anhydrous hydrofluoric acid converted gp-30 into p-25. The NH2-terminal sequence, carboxyl-terminal sequence, and the amino acid composition of several internal tryptic peptides were found to be consistent with the proposed protein sequence based upon the published sequences of hepatitis B viral DNA. The carbohydrate of gp-30 was demonstrated to be attached within the carboxyl-terminal 104 amino acids, most likely between residues 121 and 170.