TABLE 1.

HBV proteins

ProteinFunction
Envelope proteins: small
    (HBsAg), medium, largeGlycoproteins located on virion surface; bind unknown cellular receptor to initiate virion entry into host cell
Core protein (HBcAg)Encapsidates pregenomic RNA and partially double-stranded DNA genome in cytoplasm
e antigen (HBeAg)Synthesized as precursor protein; proteolytically cleaved in endoplasmic reticulum; ultimately secreted extracellularly and found in peripheral blood; has diverse activities, including immunomodulation (tolerogenic) (21) and replication inhibition (45, 76, 127)
PolymeraseReverse transcriptase, RNase H (degrades pregenomic RNA template during reverse transcription), DNA polymerase
X proteinTranscriptional transactivator; cofactor for hepatocellular carcinoma (14)