HBcAg

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HBcAg

HBcAg (core antigen) is a hepatitis B viral protein.[1][2] It is an indicator of active viral replication; this means the person infected with Hepatitis B can likely transmit the virus on to another person (i.e. the person is infectious).

Quick Facts Capsid protein, Identifiers ...
Capsid protein
Identifiers
OrganismHepatitis B virus genotype B2 (isolate Vietnam/9873/1997)
SymbolC
UniProtQ9QAB9
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StructuresSwiss-model
DomainsInterPro
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Quick Facts Hepatitis core antigen, Identifiers ...
Hepatitis core antigen
Identifiers
SymbolHepatitis_core
PfamPF00906
InterProIPR002006
CATH7abl
SCOP27abl / SCOPe / SUPFAM
Available protein structures:
Pfam  structures / ECOD  
PDBRCSB PDB; PDBe; PDBj
PDBsumstructure summary
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Thumb
Schematic overview of the hepatitis B virus particle. HBcAg is a constituent of the nucleocapsid core (green hexagon).
Thumb
The genome organisation of HBV. Some genes overlap. (ORF Core, at bottom left, encodes HBcAg.

Structure and function

HBcAg is an antigen that can be found on the surface of the nucleocapsid core (the inner most layer of the hepatitis B virus). While both HBcAg and HBeAg are made from the same open reading frame, HBcAg is not secreted as a monomer.[3] HBcAg is considered "particulate" and it does not circulate in the blood, but recent study show it can be detected in serum by Radioimmunoassay. However, it is readily detected in hepatocytes after biopsy.[4] When both HBcAg and HBeAg proteins are present, it acts as a marker of viral replication.[5]

HBcAg, also called core protein (Cp), is a 21 kDa protein of 183–185 amino acids, depending on the genotype, and is the result of the second start codon in the open reading frame.[6] Once a threshold of HBcAg proteins are translated in the cytoplasm, the viral capsid will spontaneously into a T=3 or T=4 icosahedral capsid.[7] The capsid will usually package the hepatitis B genomic RNA, but some capsids will have cellular RNA or be empty.[8] HBcAg is the target of antiviral compounds, termed capsid assembly modulators (CAMs), that are under clinical investigation for treating chronic hepatitis B.[9]

Interactions

Tapasin can interact with HBcAg18-27 and enhance cytotoxic T-lymphocyte response against HBV.[10]

See also

References

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