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Protein

Protein X

Gene

X

Organism
Hepatitis B virus genotype C subtype adr (isolate Japan/Nishioka/1983) (HBV-C)
Status
Reviewed-Annotation score: Annotation score: 3 out of 5-Experimental evidence at protein leveli

Functioni

Multifunctional protein that plays a role in silencing host antiviral defenses and promoting viral transcription. Does not seem to be essential for HBV infection. May be directly involved in development of cirrhosis and liver cancer (hepatocellular carcinoma). Most of cytosolic activities involve modulation of cytosolic calcium. The effect on apoptosis is controversial depending on the cell types in which the studies have been conducted. May induce apoptosis by localizing in mitochondria and causing loss of mitochondrial membrane potential. May also modulate apoptosis by binding host CFLAR, a key regulator of the death-inducing signaling complex (DISC). Promotes viral transcription by using the host E3 ubiquitin ligase DDB1 to target the SMC5-SMC6 complex to proteasomal degradation. This host complex would otherwise bind to viral episomal DNA, and prevents its transcription. Moderately stimulates transcription of many different viral and cellular transcription elements. Promoters and enhancers stimulated by HBx contain DNA binding sites for NF-kappa-B, AP-1, AP-2, c-EBP, ATF/CREB, or the calcium-activated factor NF-AT.UniRule annotation1 Publication

GO - Biological processi

Keywordsi

Molecular functionActivator
Biological processActivation of host NF-kappa-B by virus, Apoptosis, Host G2/M cell cycle arrest by virus, Host-virus interaction, Modulation of host cell cycle by virus, Transcription, Transcription regulation

Names & Taxonomyi

Protein namesi
Recommended name:
Protein XUniRule annotation
Alternative name(s):
HBxUniRule annotation
Peptide XUniRule annotation
pXUniRule annotation
Gene namesi
Name:XUniRule annotation
OrganismiHepatitis B virus genotype C subtype adr (isolate Japan/Nishioka/1983) (HBV-C)
Taxonomic identifieri482133 [NCBI]
Taxonomic lineageiVirusesRetro-transcribing virusesHepadnaviridaeOrthohepadnavirus
Virus hostiHomo sapiens (Human) [TaxID: 9606]
Proteomesi
  • UP000007921 Componenti: Genome

Subcellular locationi

  • Host cytoplasm UniRule annotation
  • Host nucleus UniRule annotation
  • Host mitochondrion UniRule annotation

  • Note: Mainly cytoplasmic as only a fraction is detected in the nucleus. In cytoplasm, a minor fraction associates with mitochondria or proteasomes.UniRule annotation

GO - Cellular componenti

Keywords - Cellular componenti

Host cytoplasm, Host mitochondrion, Host nucleus

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
ChainiPRO_00003199051 – 154Protein XAdd BLAST154

Post-translational modificationi

A fraction may be phosphorylated in insect cells and HepG2 cells, a human hepatoblastoma cell line. Phosphorylated in vitro by host protein kinase C or mitogen-activated protein kinase. N-acetylated in insect cells.UniRule annotation1 Publication

Interactioni

Subunit structurei

May form homodimer. May interact with host CEBPA, CFLAR, CREB1, DDB1, E4F1, HBXIP, HSPD1/HSP60, NFKBIA, POLR2E and SMAD4. Interacts with host SMC5-SMC6 complex and induces its degradation.UniRule annotation

Structurei

3D structure databases

ProteinModelPortaliP0C686.
SMRiP0C686.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Region

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Regioni68 – 117Mitochondrial targeting sequenceUniRule annotationAdd BLAST50

Sequence similaritiesi

Belongs to the orthohepadnavirus protein X family.UniRule annotation

Family and domain databases

HAMAPiMF_04074. HBV_X. 1 hit.
InterProiView protein in InterPro
IPR000236. Transactivation_prot_X.
PfamiView protein in Pfam
PF00739. X. 1 hit.

Sequencei

Sequence statusi: Complete.

P0C686-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MAARVCCQLD PARDVLCLRP VGAESRGRPV SGPFGPLPSP SSSAVPADHG
60 70 80 90 100
ARLSLRGLPV CAFSSAGPCA LRFTSARRME TTVNAHQVLP KVLHKRTLGL
110 120 130 140 150
SAMSTTDLEA YFKDCLFKDW EELGEEIRLM VFVLGGCRHK LVCSPAPCNF

FTSA
Length:154
Mass (Da):16,590
Last modified:February 26, 2008 - v1
Checksum:iC0A9C33C82143FA4
GO

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
D00630 Genomic DNA. No translation available.

Similar proteinsi

Links to similar proteins from the UniProt Reference Clusters (UniRef) at 100%, 90% and 50% sequence identity:
100%UniRef100 combines identical sequences and sub-fragments with 11 or more residues from any organism into one UniRef entry.
90%UniRef90 is built by clustering UniRef100 sequences that have at least 90% sequence identity to, and 80% overlap with, the longest sequence (a.k.a seed sequence).
50%UniRef50 is built by clustering UniRef90 seed sequences that have at least 50% sequence identity to, and 80% overlap with, the longest sequence in the cluster.

Entry informationi

Entry nameiX_HBVC1
AccessioniPrimary (citable) accession number: P0C686
Entry historyiIntegrated into UniProtKB/Swiss-Prot: February 26, 2008
Last sequence update: February 26, 2008
Last modified: July 5, 2017
This is version 38 of the entry and version 1 of the sequence. See complete history.
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programViral Protein Annotation Program

Miscellaneousi

Caution

Transcriptional activities should be taken with a grain of salt. As of 2007, all studies demonstrating in vivo interaction between protein X and transcriptional components were performed with significant overexpression of both proteins and in the absence of viral infection.

Keywords - Technical termi

Complete proteome

Documents

  1. SIMILARITY comments
    Index of protein domains and families