Structural analysis of the gene coding for hepatitis B virus surface antigen and its product

The entire genome of hepatitis B virus (subtype adr) has been cloned into pBR322. The clones could be classified into at least seven groups by their restriction endonuclease cleavage maps. The nucleotide sequences of the hepatitis B surface antigen (HBsAg)-coding regions for five clones were determined and compared with published sequences of the HBsAg gene including those of adw, ayw, adyw and adr. The 13 available versions of the amino acid sequence of the polypeptide, predicted from the nucleotide sequences, were analysed in terms of the established specificities of the HBsAg, including the four subtypes. The analysis indicated that a relatively hydrophilic region of the HBsAg protein, spanning amino acid residues 110 to 160, specifies the major (w) and (r) subtype system. The (w/r) subtype appears to depend on changes in one or more variable amino acids at positions 47, 110, 113, 126 and 160 of the HBsAg polypeptide.