P03165 · X_HBVD3
- ProteinProtein X
- GeneX
- StatusUniProtKB reviewed (Swiss-Prot)
- Amino acids154 (go to sequence)
- Protein existenceEvidence at protein level
- Annotation score5/5
Function
function
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.
GO annotations
Aspect | Term | |
---|---|---|
Cellular Component | host cell mitochondrion | |
Cellular Component | host cell nucleus | |
Biological Process | apoptotic process | |
Biological Process | DNA-templated transcription | |
Biological Process | symbiont-mediated activation of host NF-kappaB cascade | |
Biological Process | symbiont-mediated arrest of host cell cycle during G2/M transition | |
Biological Process | viral genome replication |
Keywords
- Molecular function
- Biological process
Names & Taxonomy
Protein names
- Recommended nameProtein X
- Alternative names
Gene names
Organism names
- Strain
- Taxonomic lineageViruses > Riboviria > Pararnavirae > Artverviricota > Revtraviricetes > Blubervirales > Hepadnaviridae > Orthohepadnavirus > Hepatitis B virus > hepatitis B virus genotype D
- Virus hosts
Accessions
- Primary accessionP03165
Proteomes
Subcellular Location
UniProt Annotation
GO Annotation
Note: Mainly cytoplasmic as only a fraction is detected in the nucleus. In cytoplasm, a minor fraction associates with mitochondria or proteasomes.
Keywords
- Cellular component
Phenotypes & Variants
Features
Showing features for natural variant, mutagenesis.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Natural variant | 26 | in strain: Switzerland/Strubin/1999 | ||||
Sequence: R → C | ||||||
Natural variant | 33 | in strain: Switzerland/Strubin/1999 | ||||
Sequence: S → P | ||||||
Natural variant | 36 | in strain: Switzerland/Strubin/1999 | ||||
Sequence: T → A | ||||||
Natural variant | 40-43 | in strain: Switzerland/Strubin/1999 | ||||
Sequence: PSPS → SSLP | ||||||
Natural variant | 46 | in strain: Latvia | ||||
Sequence: P → S | ||||||
Natural variant | 47-48 | in strain: Switzerland/Strubin/1999 | ||||
Sequence: TD → AA | ||||||
Mutagenesis | 77-78 | No effect on interaction with human DDB1. | ||||
Sequence: RR → EE | ||||||
Natural variant | 84-88 | in strain: Latvia | ||||
Sequence: NAHQI → KAQPF | ||||||
Mutagenesis | 91 | No effect on interaction with human DDB1. | ||||
Sequence: K → E | ||||||
Mutagenesis | 95 | No effect on interaction with human DDB1. | ||||
Sequence: K → E | ||||||
Mutagenesis | 96 | Complete loss of interaction with human DDB1. | ||||
Sequence: R → E | ||||||
Mutagenesis | 98 | Complete loss of interaction with human DDB1. | ||||
Sequence: L → F | ||||||
Natural variant | 102 | in strain: Latvia | ||||
Sequence: A → V | ||||||
Mutagenesis | 107 | No effect on interaction with human DDB1. | ||||
Sequence: D → R | ||||||
Mutagenesis | 113-114 | No effect on interaction with human DDB1. | ||||
Sequence: KD → ER |
Variants
We now provide the "Disease & Variants" viewer in its own tab.
The viewer provides 8 variants from UniProt as well as other sources including ClinVar and dbSNP.
PTM/Processing
Features
Showing features for chain.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Chain | PRO_0000222361 | 1-154 | Protein X | |||
Sequence: MAARLCCQLDPARDVLCLRPVGAESRGRPFSGSLGTLSSPSPSAVPTDHGAHLSLRGLPVCAFSSAGPCALRFTSARRMETTVNAHQILPKVLHKRTLGLSAMSTTDLEAYFKDCLFKDWEELGEEIRLKVFVLGGCRHKLVCAPAPCNFFTSA |
Post-translational modification
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.
PTM databases
Interaction
Subunit
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. Interacts with host TRPC4AP; leading to prevent ubiquitination of TRPC4AP. Interacts with host PLSCR1; this interaction promotes ubiquitination and degradation of HBx and impairs HBx-mediated cell proliferation.
Binary interactions
Type | Entry 1 | Entry 2 | Number of experiments | Intact | |
---|---|---|---|---|---|
XENO | P03165 | AKT1 P31749 | 3 | EBI-7683985, EBI-296087 | |
XENO | P03165 | Akt1 P31750 | 2 | EBI-7683985, EBI-298707 |
Protein-protein interaction databases
Family & Domains
Features
Showing features for region.
Type | ID | Position(s) | Description | |||
---|---|---|---|---|---|---|
Region | 68-117 | Mitochondrial targeting sequence | ||||
Sequence: PCALRFTSARRMETTVNAHQILPKVLHKRTLGLSAMSTTDLEAYFKDCLF |
Sequence similarities
Belongs to the orthohepadnavirus protein X family.
Family and domain databases
Sequence
- Sequence statusComplete
- Length154
- Mass (Da)16,618
- Last updated1990-04-01 v2
- Checksum29FD1CC9E09A34B5
Keywords
- Technical term