Related Experiment Videos
The duck hepatitis B virus core protein contains a highly phosphorylated C terminus that is essential for replication
H J Schlicht1, R Bartenschlager, H Schaller
1Zentrum für Molekularbiologie, Universität Heidelberg, Federal Republic of Germany.
Insights
Duck hepatitis B virus core protein (DHBcAg) exhibits heterogeneity due to C-terminal phosphorylation. Truncated DHBcAg mutants reveal insights into viral replication and assembly.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- Duck hepatitis B virus (DHBV) is a hepadnavirus with a core protein (DHBcAg) essential for viral structure and replication.
- Understanding DHBcAg post-translational modifications is crucial for deciphering viral assembly and infectivity.
Purpose of the Study:
- To biochemically and mutationally analyze the duck hepatitis B virus core protein (DHBcAg).
- To investigate the role of DHBcAg phosphorylation and C-terminal modifications in viral particle formation, genome replication, and infectivity.
Main Methods:
- Biochemical analysis of DHBV core particles to determine protein composition and heterogeneity.
- Site-directed mutagenesis to assess the impact of C-terminal amino acid deletions on DHBcAg phosphorylation and function.
- Infectivity assays in ducklings to evaluate the role of specific DHBcAg domains in viral replication.
Main Results:
- DHBV core particles contain heterogeneous DHBcAg forms (32-34 kDa) primarily due to C-terminal phosphorylation.
- Bacterial expression of DHBcAg yielded non-phosphorylated protein, indicating host cell kinase involvement.
- Deletion of the C-terminal 12 amino acids had minor effects on phosphorylation and capsid packaging but impaired infectivity.
- Deletion of the C-terminal 36 amino acids abolished heterogeneity, allowed particle formation, but resulted in replication-defective particles.
Conclusions:
- Extensive phosphorylation of the DHBcAg C terminus contributes significantly to core protein heterogeneity.
- The C terminus of DHBcAg plays a critical role in genome replication, although not essential for capsid assembly or packaging.
- Specific C-terminal domains are vital for DHBV infectivity, highlighting their importance in the viral life cycle.
Abstract:
In this report, we present biochemical and mutational analyses of the duck hepatitis B virus core protein (DHBcAg). The data show that duck hepatitis B virus core particles consist of at least four different proteins with sizes between 32 and 34 kilodaltons, all of which react with DHBcAg-specific antiserum. Most of the heterogeneity was found to be due to extensive phosphorylation of the DHBcAg C terminus. Bacterially synthesized DHBcAg was not phosphorylated, and mutations within the viral P gene did not influence phosphorylation, suggesting that the kinase activity is not encoded by the viral C or P gene. Removal of the last 12 C-terminal DHBcAg amino acids, which are at least in part located on the core particle surface, had only a minor effect on DHBcAg phosphorylation and did not interfere with packaging of the capsids into viral envelopes or with genome replication. However, an attempt to infect ducklings with this mutant failed. Removal of the last 36 C-terminal DHBcAg amino acids abolished core protein heterogeneity but did not prevent particle formation. Interestingly, these particles were defective in genome replication, although they could still package viral pregenomic RNA.