Characteristics of pre-S2 region of hepatitis B virus.

The nucleotide sequence of our cloned HBV DNA (subtype adw) has been determined. When the 165-nucleotide sequence of the pre-S2 region was compared with 7 other published sequences (subtypes adw, adr, ayw, and adyw), we found 38 nucleotide substitutions among different subtypes and 4 (adr) or 6 (adw and ayw) substitutions within the same subtype. Analysis of the predicted amino acid sequence from the known nucleotide sequences indicates that: there are 20 amino acid substitutions, the longest conserved amino acid sequence is located between amino acids 23 to 34, and the 54th amino acid is identical within the same subtype but varies in different subtypes.