The HBV (hepatitis B virus) core is a phosphoprotein whose assembly, replication, encapsidation and localization are regulated by phosphorylation. It is known that PKC (protein kinase C) regulates pgRNA (pregenomic RNA) encapsidation by phosphorylation of the C-terminus of core, which is a component packaged into capsid. Neither the N-terminal residue phosphorylated by PKC nor the role of the C-terminal phosphorylation have been cleary defined. In the present study we found that HBV Cp149 (core protein C-terminally truncated at amino acid 149) expressed in Escherichia coli was phosphorylated by PKC at Ser106. PKC-mediated phosphorylation increased core affinity, as well as assembly and capsid stability. In vitro phosphorylation with core mutants (S26A, T70A, S106A and T114A) revealed that the Ser106 mutation inhibited phosphorylation of core by PKC. CD analysis also revealed that PKC-mediated phosphorylation stabilized the secondary structure of capsid. When either pCMV/FLAG-Cp149[WT (wild-type)] or pCMV/FLAG-S106A Cp149 was transfected into Huh7 human hepatoma cells, mutant capsid level was decreased by 2.06-fold with the S106A mutant when compared with WT, although the same level of total protein was expressed in both cases. In addition, when pUC1.2x and pUC1.2x/S106A were transfected, mutant virus titre was decreased 2.31-fold compared with WT virus titre. In conclusion, PKC-mediated phosphorylation increased capsid assembly, stability and structural stability.
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Research Article|
October 28 2008
Phosphorylation of hepatitis B virus core C-terminally truncated protein (Cp149) by PKC increases capsid assembly and stability
Hang Kang
;
Hang Kang
*School of Biological Sciences, Seoul National University, Shillim-dong, Seoul 151-742, Korea
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Jaehoon Yu
;
Jaehoon Yu
†Department of Chemistry Education, Seoul National University, Shillim-dong, Seoul 151-742, Korea
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Guhung Jung
Guhung Jung
1
*School of Biological Sciences, Seoul National University, Shillim-dong, Seoul 151-742, Korea
1To whom correspondence should be addressed (email drjung@snu.ac.kr).
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Biochem J (2008) 416 (1): 47–54.
Article history
Received:
April 07 2008
Revision Received:
July 02 2008
Accepted:
July 08 2008
Accepted Manuscript online:
July 08 2008
Citation
Hang Kang, Jaehoon Yu, Guhung Jung; Phosphorylation of hepatitis B virus core C-terminally truncated protein (Cp149) by PKC increases capsid assembly and stability. Biochem J 15 November 2008; 416 (1): 47–54. doi: https://doi.org/10.1042/BJ20080724
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