Glycopeptide composition of hepatitis B surface antigen.

Three major polypeptides of hepatitis B surface antigen (HBsAg), with mol. wt. 22,000 (p22), 27,000 (p27) and 68,000 (p68), were separated by preparative SDS-PAGE. These three peptides as well as intact HBsAg were found to have almost identical amino acid compositions and carbohydrate was detected in p27 and p68 by PAS staining. Papain treatment of p68 produced two distinct peptides p27 and p22. Moreover, when an artificial mixture of p27 and p22 in a ratio of 1:1 was treated with 0.2 M-periodate for 30 min at 37 degrees C, only p22 was detectable. These results suggest that p68 is composed of p27 and p22, and that p27 is a glycosylated product of p22. Thus, from the evidence obtained, it is possible that p22 (22,000 peptide) is the minimum size of the unique hepatitis B virus (HBV) gene product involved.