B3IWX1 · B3IWX1_HBV

Function

function

Multifunctional enzyme that converts the viral RNA genome into dsDNA in viral cytoplasmic capsids. This enzyme displays a DNA polymerase activity that can copy either DNA or RNA templates, and a ribonuclease H (RNase H) activity that cleaves the RNA strand of RNA-DNA heteroduplexes in a partially processive 3'- to 5'-endonucleasic mode. Neo-synthesized pregenomic RNA (pgRNA) are encapsidated together with the P protein, and reverse-transcribed inside the nucleocapsid. Initiation of reverse-transcription occurs first by binding the epsilon loop on the pgRNA genome, and is initiated by protein priming, thereby the 5'-end of -DNA is covalently linked to P protein. Partial +DNA is synthesized from the -DNA template and generates the relaxed circular DNA (RC-DNA) genome. After budding and infection, the RC-DNA migrates in the nucleus, and is converted into a plasmid-like covalently closed circular DNA (cccDNA). The activity of P protein does not seem to be necessary for cccDNA generation, and is presumably released from +DNA by host nuclear DNA repair machinery.

Miscellaneous

Hepadnaviral virions contain probably just one P protein molecule per particle.

Caution

Lacks conserved residue(s) required for the propagation of feature annotation.

Catalytic activity

Activity regulation

Activated by host HSP70 and HSP40 in vitro to be able to bind the epsilon loop of the pgRNA. Because deletion of the RNase H region renders the protein partly chaperone-independent, the chaperones may be needed indirectly to relieve occlusion of the RNA-binding site by this domain. Inhibited by several reverse-transcriptase inhibitors: Lamivudine, Adefovir and Entecavir.

Features

Showing features for site, binding site.

TypeIDPosition(s)Description
Site63Priming of reverse-transcription by covalently linking the first nucleotide of the -DNA
Binding site428Mg2+ (UniProtKB | ChEBI); catalytic
Binding site550Mg2+ (UniProtKB | ChEBI); catalytic
Binding site551Mg2+ (UniProtKB | ChEBI); catalytic

GO annotations

AspectTerm
Molecular FunctionDNA binding
Molecular FunctionDNA-directed DNA polymerase activity
Molecular Functionmetal ion binding
Molecular FunctionRNA-directed DNA polymerase activity
Molecular FunctionRNA-DNA hybrid ribonuclease activity
Biological ProcessDNA replication
Biological Processsymbiont-mediated suppression of host innate immune response
Biological Processvirus-mediated perturbation of host defense response

Keywords

Names & Taxonomy

Protein names

  • Recommended name
    Protein P

Including 3 domains:

  • Recommended name
    DNA-directed DNA polymerase
  • EC number
  • Recommended name
    RNA-directed DNA polymerase
  • EC number
  • Recommended name
    Ribonuclease H
  • EC number

Gene names

    • Name
      P

Organism names

Accessions

  • Primary accession
    B3IWX1

Proteomes

Family & Domains

Features

Showing features for region, compositional bias, domain.

TypeIDPosition(s)Description
Region1-177Terminal protein domain (TP)
Region184-234Disordered
Compositional bias194-234Polar residues
Region346-689Polymerase/reverse transcriptase domain (RT)
Domain356-599Reverse transcriptase

Domain

Terminal protein domain (TP) is hepadnavirus-specific. Spacer domain is highly variable and separates the TP and RT domains. Polymerase/reverse-transcriptase domain (RT) and ribonuclease H domain (RH) are similar to retrovirus reverse transcriptase/RNase H.
The polymerase/reverse transcriptase (RT) and ribonuclease H (RH) domains are structured in five subdomains: finger, palm, thumb, connection and RNase H. Within the palm subdomain, the 'primer grip' region is thought to be involved in the positioning of the primer terminus for accommodating the incoming nucleotide. The RH domain stabilizes the association of RT with primer-template.

Sequence similarities

Belongs to the hepadnaviridae P protein family.

Family and domain databases

Sequence

  • Sequence status
    Complete
  • Length
    842
  • Mass (Da)
    94,671
  • Last updated
    2008-09-02 v1
  • Checksum
    6988EA26A3029F74
MPLSYQHFRRLLLLDEEAGPLEEELPRLADEDLNRRVAEDLHLQLPNVSIPWTHKVGNFTGLYSSTIPVFNPDWQTPSFPNIHLHQDIITKCEQFVGPLTVNEKRRLKLVMPARFFPNSTKYLPLDKGIKPYYPENVVNHYFQTRHYLHTLWKAGILYKRETSRSASFCGSPYTWEQDLQHGAFLDGPSRVGKEPFHQQSSRIPSRSPVGPSIQSKYQQSRLGLQSQKGPLARGQQGRSWSLWTRVHPSTRRPFGVEPSVSGHTNNFASRSASCLHQSSVREAAYSHLSTTKRQSSSGHAVELYSIPPSSTKSQSQGPVFSCWWLQFRDSEPCSDYCLSHLVNLLQDWGPCTEHGEHHIRIPRTPARVTGGVFLVDKNPHNTAESRLVVDFSQFSRGSARVSWPKFAVPNLQSLTNLLSSNLSWLSLDVSAAFYHIPLHPAAMPHLLVGSSGLSRYVARLSSDSRILDHQYGTLQNLHDSCSRQLYVSLMLLYKTFGRKLHLYSHPIILGFRKIPMGVGLSPFLLAQFTSAICSVVRRAFPHCLAFSYMDDVVLGAKSVQHLESLYTAVTNFLLSLGIHLNPNKTKRWGYSLXFMGYVIGSWGTLPQEHITQKIKXCFRKLPVNRPIDWKVCQRITGLLGFAAPFTQCGYPALMPLYACIQAKQAFTFSPTYKAFLCKQYMNLYPVARQRPGLCQVFADATPTGWGLAIGHQRMRGTFVAPLPIHTAELLAACFARSRSGAKLIGTDNSVVLSRKYTSFPWLLGCAANWILRGTSFVYVPSALNPADDPSRGRLGLCRPLLRLPFLPTTGRTSLYAVSPSVPSHLPDRVHFASPLHVTWKPP

Features

Showing features for compositional bias.

TypeIDPosition(s)Description
Compositional bias194-234Polar residues

Sequence databases

Nucleotide SequenceProtein SequenceMolecule TypeStatus
AB375165
EMBL· GenBank· DDBJ
BAG50279.1
EMBL· GenBank· DDBJ
Genomic DNA

Similar Proteins

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