P03146 (CAPSD_HBVD3) Reviewed, UniProtKB/Swiss-Prot

Names and origin

Protein names

Recommended name:
Capsid protein

Alternative name(s):
Core antigen
Core protein
HBcAg
p21.5

Gene names

Name:

C

Organism

Hepatitis B virus genotype D subtype ayw (isolate France/Tiollais/1979) (HBV-D) [Complete proteome]

Taxonomic identifier

490133 [NCBI]

Taxonomic lineage

Viruses › Retro-transcribing viruses › Hepadnaviridae › Orthohepadnavirus

Virus host

Pan troglodytes (Chimpanzee) [TaxID: 9598]
Homo sapiens (Human) [TaxID: 9606]

Protein attributes

Sequence length	183 AA.
Sequence status	Complete.
Protein existence	Evidence at protein level

General annotation (Comments)

Function	Self assembles to form an icosahedral capsid. Most capsid appear to be large particles with a icosahedral symmetry of T=4 and consist of 240 copies of capsid protein, though a fraction forms smaller T=3 particles consisting of 180 capsid proteins. Entering capsid are transported along microtubules to the nucleus. Phosphorylation of the capsid is thought to induce exposure of nuclear localization signal in the C-terminal portion of the capsid protein that allows binding to the nuclear pore complex via the importin (karyopherin-) alpha and beta. Capsids are imported in intact form through the nuclear pore into the nuclear basket, where it probably binds NUP153. Only capsids that contain the mature viral genome can release the viral DNA and capsid protein into the nucleoplasm. Immature capsids get stucked in the basket. Capsids encapsulate the pre-genomic RNA and the P protein. Pre-genomic RNA is reverse transcribed into DNA while the capsid is still in the cytoplasm. The capsid can then either be directed to the nucleus, providing more genome for transcription, or bud through the endoplasmic reticulum to provide new virions By similarity. Encapsidates hepatitis delta genome By similarity.
Subunit structure	Homodimerizes, then multimerizes. Interacts with cytosol exposed regions of viral L glycoprotein present in the reticulum-to-Golgi compartment. Interacts with human FLNB By similarity.
Subcellular location	Capsid protein: Virion. Host cytoplasm By similarity.
Post-translational modification	Phosphorylated by host SRPK1, SRPK2, and maybe protein kinase A, protein kinase C or GAPDH. Phosphorylation is critical for pregenomic RNA packaging. Protein kinase C phosphorylation is stimulated by HBx protein and may play a role in transport of the viral genome to the nucleus at the late step during viral replication cycle. Protein kinase A phosphorylation may promote capsid assembly By similarity. Ref.4 Ref.6
Sequence similarities	Belongs to the orthohepadnavirus core antigen family.
Sequence caution	The sequence CAA24706.1 differs from that shown. Reason: Erroneous initiation.

Ontologies

Keywords
Biological process	Cytoplasmic active transport of viral material Host-virus interaction Initiation of viral infection Microtubule-dependent active transport of viral material Viral penetration into host nucleus
Cellular component	Host cytoplasm Virion
Coding sequence diversity	Alternative initiation
Domain	Repeat
Ligand	DNA-binding RNA-binding
Molecular function	Capsid protein T=4 icosahedral capsid protein
PTM	Phosphoprotein
Technical term	Complete proteome
Gene Ontology (GO)
Biological process	interspecies interaction between organisms Inferred from electronic annotation. Source: UniProtKB-KW pathogenesis Inferred from electronic annotation. Source: InterPro
Cellular component	host cell cytoplasm Inferred from electronic annotation. Source: UniProtKB-SubCell viral capsid Inferred from electronic annotation. Source: UniProtKB-KW
Molecular function	DNA binding Inferred from electronic annotation. Source: UniProtKB-KW RNA binding Inferred from electronic annotation. Source: UniProtKB-KW structural molecule activity Inferred from electronic annotation. Source: InterPro
Complete GO annotation...

Alternative products

This entry describes 2 isoforms produced by alternative initiation. [Align] [Select]

Isoform Capsid protein (identifier: P03146-1)

This isoform has been chosen as the 'canonical' sequence. All positional information in this entry refers to it. This is also the sequence that appears in the downloadable versions of the entry.

Isoform External core antigen (identifier: P0C573-1)

The sequence of this isoform can be found in the external entry P0C573.
Isoforms of the same protein are often annotated in two different entries if their sequences differ significantly.

Sequence annotation (Features)

	Feature key	Position(s)	Length	Description	Graphical view	Feature identifier
Molecule processing
	Chain	1 – 183	183	Capsid protein		PRO_0000222315
Regions
	Repeat	155 – 161	7	1; half-length
	Repeat	162 – 169	8	2
	Repeat	170 – 177	8	3
	Region	155 – 177	23	3 X 8 AA repeats of S-P-R-R-R-[PR]-S-Q
	Region	177 – 183	7	RNA binding By similarity
	Motif	158 – 175	18	Bipartite nuclear localization signal Potential
Amino acid modifications
	Modified residue	87	1	Phosphoserine; by host PKA By similarity
	Modified residue	155	1	Phosphoserine; by host
	Modified residue	162	1	Phosphoserine; by host
	Modified residue	170	1	Phosphoserine; by host
Natural variations
	Natural variant	33	1	T → N in strain: Latvia.
	Natural variant	80	1	A → I in strain: Latvia.
	Natural variant	97	1	F → L Frequent mutation in chronic HBV carriers.
Experimental info
	Mutagenesis	155	1	S → A: Complete loss of replication. Ref.7
	Mutagenesis	162	1	S → A: Complete loss of pregenomic RNA encapsidation and replication. Ref.7
	Mutagenesis	170	1	S → A: Partial loss of replication. Ref.7

Sequences

	Sequence		Length	Mass (Da)
	Isoform Capsid protein [UniParc]. Last modified July 21, 1986. Version 1. Checksum: E0D9D9763F24E958	FASTA	183	21,116
	10 20 30 40 50 60 MDIDPYKEFG ATVELLSFLP SDFFPSVRDL LDTASALYRE ALESPEHCSP HHTALRQAIL 70 80 90 100 110 120 CWGELMTLAT WVGVNLEDPA SRDLVVSYVN TNMGLKFRQL LWFHISCLTF GRETVIEYLV 130 140 150 160 170 180 SFGVWIRTPP AYRPPNAPIL STLPETTVVR RRGRSPRRRT PSPRRRRSQS PRRRRSQSRE SQC
	Isoform External core antigen [UniParc]. See P0C573.		–	–

References

[1]	"Nucleotide sequence of the hepatitis B virus genome (subtype ayw) cloned in E. coli." Galibert F., Mandart E., Fitoussi F., Tiollais P., Charnay P. Nature 281:646-650(1979) [PubMed: 399327] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA].
[2]	"Subtype ayw variant of hepatitis B virus. DNA primary structure analysis." Bichko V., Pushko P., Dreilina D., Pumpen P., Gren E.Y. FEBS Lett. 185:208-212(1985) [PubMed: 3996597] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA]. Strain: Latvia.
[3]	"Evolutionary conservation in the hepatitis B virus core structure: comparison of human and duck cores." Kenney J.M., von Bonsdorff C.H., Nassal M., Fuller S.D. Structure 3:1009-1019(1995) [PubMed: 8589996] [Abstract] Cited for: CAPSID STRUCTURE.
[4]	"Phosphorylation of the core protein of hepatitis B virus by a 46-kilodalton serine kinase." Kau J.H., Ting L.P. J. Virol. 72:3796-3803(1998) [PubMed: 9557662] [Abstract] Cited for: PHOSPHORYLATION.
[5]	"Subtype-independent immature secretion and subtype-dependent replication deficiency of a highly frequent, naturally occurring mutation of human hepatitis B virus core antigen." Yuan T.T., Tai P.C., Shih C. J. Virol. 73:10122-10128(1999) [PubMed: 10559327] [Abstract] Cited for: NATURALLY OCCURRING MUTATION.
[6]	"Identification of SRPK1 and SRPK2 as the major cellular protein kinases phosphorylating hepatitis B virus core protein." Daub H., Blencke S., Habenberger P., Kurtenbach A., Dennenmoser J., Wissing J., Ullrich A., Cotten M. J. Virol. 76:8124-8137(2002) [PubMed: 12134018] [Abstract] Cited for: PHOSPHORYLATION.
[7]	"Hepatitis B virus DNA replication is coordinated by core protein serine phosphorylation and HBx expression." Melegari M., Wolf S.K., Schneider R.J. J. Virol. 79:9810-9820(2005) [PubMed: 16014942] [Abstract] Cited for: MUTAGENESIS OF SER-155; SER-162 AND SER-170.
[8]	"Envelopment of the hepatitis B virus nucleocapsid." Bruss V. Virus Res. 106:199-209(2004) [PubMed: 15567498] [Abstract] Cited for: REVIEW.
+	Additional computationally mapped references.

Web resources

HepSEQ

Hepatitis virus B database

Cross-references

Sequence databases
EMBL GenBank DDBJ	V01460 Genomic DNA. Translation: CAA24706.1. Different initiation. X02496 Genomic DNA. No translation available.
3D structure databases
ProteinModelPortal	P03146.
SMR	P03146. Positions 1-143.
ModBase	Search...
Protocols and materials databases
StructuralBiologyKnowledgebase	Search...
Family and domain databases
InterPro	IPR002006. Viral_capsid_core_Hepatitis. [Graphical view]
Pfam	PF00906. Hepatitis_core. 1 hit. [Graphical view]
SUPFAM	SSF47852. Viral_capsid_core_Hepatitis. 1 hit.
ProtoNet	Search...

Entry information

Entry name

CAPSD_HBVD3

Accession

Primary (citable) accession number: P03146

Entry history

Integrated into UniProtKB/Swiss-Prot:	July 21, 1986
Last sequence update:	July 21, 1986
Last modified:	May 31, 2011
This is version 65 of the entry and version 1 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation program

Viral Protein Annotation Program