Structure of hepatitis B surface antigen. Correlation of subtype with amino acid sequence and location of the carbohydrate moiety.

Hepatitis B surface antigens (HBsAg) of both the adw and ayw subtypes have been purified from four different sources. These antigens have been compared by comparison of the products of tryptic hydrolysis performed under conditions which do not disrupt the overall particle morphology of HBsAg. The resultant peptides were compared by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and high performance liquid chromatography followed by amino acid analysis and Edman degradation of the isolated peptides. The same techniques were also applied to HBsAg which had been labeled with tritium in the carbohydrate moiety of the glycoprotein gp-30. These studies demonstrate that residues 122-150 of the protein p-25 and glycoprotein gp-30 occupy an exposed region of the HBsAg lipoprotein particle and contain the major attachment site for carbohydrate in the case of gp-30. The two subtypes were found to differ at two specific positions in this region, suggesting that this is an antigenically important area of the protein.