ABSTRACT
This chapter discusses the biosynthesis and enzymatic functions of the hepadnaviral reverse transcriptase. It summarizes the data on the biosynthesis and enzymatic functions of the hepadnaviral reverse transcriptase. Each reverse transcriptase must be endowed with three different enzymatic activities: an RNA-dependent DNA polymerase, a DNA-dependent DNA polymerase, and an RNase H activity. The chapter describes the structure of the polymerase gene and its expression strategy. An analyses carried out with antisera specific for individual domains of the Duck hepatitis B virus Protein gene product demonstrated that this genome-linked protein, or DNA terminal protein, is derived from the N-terminal domain of the polymerase protein. The genome of the human hepatitis B virus (HBV), the prototype member of the mammalian hepadnaviruses, contains four open reading frames that can code for protein. Hepadnaviral reverse transcriptase is not synthesized as a core/polymerase fusion protein and therefore cannot be incorporated into a nascent capsid by coassembly of such fusion proteins with core protein molecules.
