Segmental homology and internal repetitiousness identified in putative nucleic acid polymerase and human hepatitis B surface antigen of human hepatitis B virus.

In a previous paper, it was argued that only those coding sequences descended from oligomeric repeats (the number of bases in the oligomeric unit not being a multiple of 3) can retain sufficiently long alternative open reading frames, and that such alternative open reading frames serve as the reservoir for the sudden generation of new polypeptide chains with novel functions. It was suggested that plasmid-encoded 6-amino hexanoic acid linear oligomer hydrolase that suddenly endowed Flavobacterium sp. K172 with the capacity to live off nylon by-products arose by the above mechanism. A corollary to the above argument is the expectation that those viral base sequences that are known to use two of the three alternative reading frames to encode two different polypeptide chains should invariably contain recognizable remains of the oligomeric tandem repeats, and as a consequence, various oligopeptidic repeats should also be present in the amino acid sequence of each. Furthermore, two polypeptide chains encoded by the same base sequence translated in different reading frames should show segmental homology of the type depicted previously. In the present paper, the base sequence of human hepatitis B virus ayw subtype that encodes an 832 amino acid residue long putative nucleic acid polymerase in one reading frame and a 226 residue long human hepatitis B surface antigen in the other reading frame was examined. All three predictions noted above were satisfied.