STRUCTURE AND GLYCOSYLATION PATTERNS OF SURFACE-PROTEINS FROM WOODCHUCK HEPATITIS-VIRUS

Woodchucks chronically infected with woodchuck hepatitis virus (WHV) a re a valuable model for human hepatitis B virus (HBV) in studies of pa thogenesis, immunity, and antiviral therapy. For this reason, substant ial efforts to characterize both the similarities and the differences between HBV and WHV are being made. The structure of the WHV surface p roteins (WHs proteins) has not yet been adequately elucidated. The ban ds that would be expected for glycosylated and nonglycosylated small ( S) WHs protein are found by sodium dodecyl sulfate gel electrophoresis of purified WHs protein, but the bands corresponding to the middle (M ) and large (L) WHs proteins of HBV are not seen at the expected sizes , even though the sequences of the WHV and HBV surface protein genes a re 60% homologous. By amino-terminal sequencing we have identified two bands at 41 and 45 kDa as the MWHs proteins, 8 kDa larger than expect ed. We have also confirmed that two bands at 24 and 27 kDa are SWHs pr oteins. A protein of 49 kDa was blocked at the N terminus, which using immunoblotting with an antiserum against WHV pre-SI (positions 126 to 146) was identified, together with a part of the 45-kDa protein, as g lycosylated and nonglycosylated LWHs protein of the expected size. Sia lidase and O-glycosidase digestion showed that the larger size of MWHs protein results from the presence of O glycoside groups which are pro bably in the pre-SZ domain of MWHs protein. Since the pre-S2 domains o f HBV and WW have similar numbers of potential O glycosylation sites, it appears to be likely that the glycosyl-transferases act differently on the viral proteins in woodchucks and humans.