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Protein

Fusion glycoprotein F0

Gene

F

Organism
Human respiratory syncytial virus A (strain A2)
Status
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli

Functioni

During virus entry, induces fusion of viral and cellular membranes leading to delivery of the nucleocapsid into the cytoplasm. The fusogenic activity is inactive untill entry into host cell endosome, where a furin-like protease cleaves off a small peptide between F1 and F2 (PubMed:18216092). Interacts directly with heparan sulfate and may participates in virus attachment (PubMed:10864656). Furthermore, the F2 subunit was identifed as the major determinant of RSV host cell specificity (PubMed:11493675). Later in infection, proteins F expressed at the plasma membrane of infected cells can mediate fusion with adjacent cells to form syncytia, a cytopathic effect that could lead to tissue necrosis. The fusion protein is also able to trigger p53-dependent apoptosis (PubMed:12663767).5 Publications

Sites

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sitei109 – 1102Cleavage; by host1 Publication
Sitei136 – 1372Cleavage; by host furin1 Publication

GO - Biological processi

Complete GO annotation...

Keywords - Biological processi

Fusion of virus membrane with host cell membrane, Fusion of virus membrane with host membrane, Syncytium formation induced by viral infection, Viral penetration into host cytoplasm, Virus entry into host cell

Protein family/group databases

TCDBi1.G.2.1.3. the viral pore-forming membrane fusion protein-2 (vmfp2) family.

Names & Taxonomyi

Protein namesi
Recommended name:
Fusion glycoprotein F0
Short name:
Protein F
Cleaved into the following 4 chains:
Fusion glycoprotein F2'1 Publication
Interchain peptide1 Publication
Gene namesi
Name:F
OrganismiHuman respiratory syncytial virus A (strain A2)
Taxonomic identifieri11259 [NCBI]
Taxonomic lineageiVirusesssRNA virusesssRNA negative-strand virusesMononegaviralesParamyxoviridaePneumovirinaePneumovirus
Virus hostiHomo sapiens (Human) [TaxID: 9606]
ProteomesiUP000007678 Componenti: Genome

Subcellular locationi

Topology

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Topological domaini27 – 529503Extracellular1 PublicationAdd
BLAST
Transmembranei530 – 55021HelicalSequence AnalysisAdd
BLAST
Topological domaini551 – 57424Cytoplasmic1 PublicationAdd
BLAST

GO - Cellular componenti

Complete GO annotation...

Keywords - Cellular componenti

Host cell membrane, Host membrane, Membrane, Viral envelope protein, Virion

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Signal peptidei1 – 2525Sequence AnalysisAdd
BLAST
Chaini26 – 574549Fusion glycoprotein F0PRO_0000039234Add
BLAST
Chaini26 – 136111Fusion glycoprotein F21 PublicationPRO_0000039235Add
BLAST
Chaini26 – 10984Fusion glycoprotein F2'1 PublicationPRO_0000432663Add
BLAST
Peptidei110 – 13627Interchain peptide1 PublicationPRO_0000432664Add
BLAST
Chaini137 – 574438Fusion glycoprotein F1PRO_0000039236Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Glycosylationi27 – 271N-linked (GlcNAc...); by hostSequence Analysis
Disulfide bondi69 ↔ 212Interchain (between F2 and F1 chains)By similarity
Glycosylationi70 – 701N-linked (GlcNAc...); by hostSequence Analysis
Glycosylationi116 – 1161N-linked (GlcNAc...); by hostSequence Analysis
Glycosylationi126 – 1261N-linked (GlcNAc...); by hostSequence Analysis
Disulfide bondi358 ↔ 367By similarity
Disulfide bondi382 ↔ 393By similarity
Glycosylationi500 – 5001N-linked (GlcNAc...); by hostSequence Analysis
Lipidationi550 – 5501S-palmitoyl cysteine; by host1 Publication

Post-translational modificationi

The F glycoprotein is synthesized as a F0 inactive precursor that is heavily N-glycosylated and processed by host cell furin in the Golgi to yield the mature F1 and F2 proteins (PubMed:11369882). The cleavage site between F1 and F2 requires the minimal sequence [KR]-X-[KR]-R. During entry a furin-like protease cleaves F2 into F2' and a small peptide, leading to the activation of fusogenic function (PubMed:23593008).2 Publications

Keywords - PTMi

Cleavage on pair of basic residues, Disulfide bond, Glycoprotein, Lipoprotein, Palmitate

Interactioni

Subunit structurei

Homotrimer (PubMed:10846072). Interacts with glycoprotein G (PubMed:18036342). Interacts with host RHOA; this interaction facilitates virus-induced syncytium formation (PubMed:10438814).4 Publications

Protein-protein interaction databases

DIPiDIP-48772N.

Structurei

Secondary structure

1
574
Legend: HelixTurnBeta strand
Show more details
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Beta strandi29 – 335Combined sources
Turni34 – 374Combined sources
Beta strandi38 – 4912Combined sources
Beta strandi51 – 6010Combined sources
Helixi74 – 9825Combined sources
Helixi139 – 1413Combined sources
Helixi149 – 15810Combined sources
Helixi160 – 20142Combined sources
Helixi204 – 2063Combined sources
Beta strandi208 – 2114Combined sources
Helixi217 – 23923Combined sources
Turni240 – 2423Combined sources
Beta strandi243 – 2464Combined sources
Turni249 – 2513Combined sources
Helixi254 – 26310Combined sources
Beta strandi264 – 2663Combined sources
Helixi268 – 2769Combined sources
Helixi278 – 2836Combined sources
Beta strandi286 – 2927Combined sources
Beta strandi294 – 30512Combined sources
Beta strandi307 – 31812Combined sources
Beta strandi326 – 3294Combined sources
Beta strandi333 – 3364Combined sources
Beta strandi340 – 3456Combined sources
Beta strandi348 – 3536Combined sources
Helixi355 – 3573Combined sources
Beta strandi358 – 3614Combined sources
Beta strandi364 – 3685Combined sources
Helixi369 – 3713Combined sources
Beta strandi373 – 3753Combined sources
Helixi377 – 3804Combined sources
Helixi381 – 3844Combined sources
Beta strandi386 – 3883Combined sources
Beta strandi389 – 3913Combined sources
Beta strandi394 – 3985Combined sources
Beta strandi404 – 4074Combined sources
Beta strandi409 – 4168Combined sources
Beta strandi422 – 4265Combined sources
Turni427 – 4293Combined sources
Beta strandi430 – 4345Combined sources
Beta strandi437 – 4448Combined sources
Beta strandi449 – 4524Combined sources
Beta strandi455 – 4584Combined sources
Beta strandi466 – 4694Combined sources
Helixi474 – 4774Combined sources
Turni480 – 4823Combined sources
Helixi487 – 51428Combined sources

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
3IXTX-ray2.75C/P254-277[»]
3KPEX-ray1.47A159-209[»]
B482-520[»]
3O41X-ray1.95C/P423-436[»]
3O45X-ray2.87C/P423-438[»]
3RKIX-ray3.20A/B/C1-524[»]
3RRRX-ray2.82A/C/E/G/I/M26-109[»]
B/D/F/H/L/N147-513[»]
3RRTX-ray3.20A/C/E26-109[»]
B/D/F147-513[»]
4CCFX-ray2.65A/B/C/D/E/F1-574[»]
4JHWX-ray3.60F26-513[»]
4MMQX-ray3.25A26-107[»]
B137-513[»]
4MMRX-ray3.10A26-107[»]
B137-513[»]
4MMSX-ray2.40A/C/E26-107[»]
B/D/F137-513[»]
4MMTX-ray3.05A26-107[»]
B137-513[»]
4MMUX-ray3.00A26-107[»]
B137-513[»]
4MMVX-ray2.81A26-107[»]
B137-513[»]
ProteinModelPortaliP03420.
SMRiP03420. Positions 158-207, 477-516.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiP03420.

Family & Domainsi

Region

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Regioni137 – 15721Fusion peptideBy similarityAdd
BLAST

Coiled coil

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Coiled coili155 – 18329Sequence AnalysisAdd
BLAST
Coiled coili491 – 51626Sequence AnalysisAdd
BLAST

Sequence similaritiesi

Keywords - Domaini

Coiled coil, Signal, Transmembrane, Transmembrane helix

Family and domain databases

InterProiIPR000776. Fusion_F0_Paramyxovir.
[Graphical view]
PfamiPF00523. Fusion_gly. 1 hit.
[Graphical view]

Sequencei

Sequence statusi: Complete.

Sequence processingi: The displayed sequence is further processed into a mature form.

P03420-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MELLILKANA ITTILTAVTF CFASGQNITE EFYQSTCSAV SKGYLSALRT
60 70 80 90 100
GWYTSVITIE LSNIKENKCN GTDAKVKLIK QELDKYKNAV TELQLLMQST
110 120 130 140 150
PPTNNRARRE LPRFMNYTLN NAKKTNVTLS KKRKRRFLGF LLGVGSAIAS
160 170 180 190 200
GVAVSKVLHL EGEVNKIKSA LLSTNKAVVS LSNGVSVLTS KVLDLKNYID
210 220 230 240 250
KQLLPIVNKQ SCSISNIETV IEFQQKNNRL LEITREFSVN AGVTTPVSTY
260 270 280 290 300
MLTNSELLSL INDMPITNDQ KKLMSNNVQI VRQQSYSIMS IIKEEVLAYV
310 320 330 340 350
VQLPLYGVID TPCWKLHTSP LCTTNTKEGS NICLTRTDRG WYCDNAGSVS
360 370 380 390 400
FFPQAETCKV QSNRVFCDTM NSLTLPSEIN LCNVDIFNPK YDCKIMTSKT
410 420 430 440 450
DVSSSVITSL GAIVSCYGKT KCTASNKNRG IIKTFSNGCD YVSNKGMDTV
460 470 480 490 500
SVGNTLYYVN KQEGKSLYVK GEPIINFYDP LVFPSDEFDA SISQVNEKIN
510 520 530 540 550
QSLAFIRKSD ELLHNVNAGK STTNIMITTI IIVIIVILLS LIAVGLLLYC
560 570
KARSTPVTLS KDQLSGINNI AFSN
Length:574
Mass (Da):63,453
Last modified:July 21, 1986 - v1
Checksum:iA4066D9DC98933AA
GO

Natural variant

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Natural varianti102 – 1021P → A in strain: Cold-passage attenuated.
Natural varianti218 – 2181E → A in strain: Cold-passage attenuated.
Natural varianti379 – 3791I → V in strain: Cold-passage attenuated.
Natural varianti447 – 4471M → V in strain: Cold-passage attenuated.
Natural varianti523 – 5231T → I in strain: Cold-passage attenuated.

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
M11486 Genomic RNA. Translation: AAB59858.1.
U50362 Genomic RNA. Translation: AAB86664.1.
U50363 Genomic RNA. Translation: AAB86676.1.
AF035006 Genomic RNA. Translation: AAC14902.1.
U63644 Genomic RNA. Translation: AAC55970.1.
PIRiA04035. VGNZA2.
B28929.

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
M11486 Genomic RNA. Translation: AAB59858.1.
U50362 Genomic RNA. Translation: AAB86664.1.
U50363 Genomic RNA. Translation: AAB86676.1.
AF035006 Genomic RNA. Translation: AAC14902.1.
U63644 Genomic RNA. Translation: AAC55970.1.
PIRiA04035. VGNZA2.
B28929.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
3IXTX-ray2.75C/P254-277[»]
3KPEX-ray1.47A159-209[»]
B482-520[»]
3O41X-ray1.95C/P423-436[»]
3O45X-ray2.87C/P423-438[»]
3RKIX-ray3.20A/B/C1-524[»]
3RRRX-ray2.82A/C/E/G/I/M26-109[»]
B/D/F/H/L/N147-513[»]
3RRTX-ray3.20A/C/E26-109[»]
B/D/F147-513[»]
4CCFX-ray2.65A/B/C/D/E/F1-574[»]
4JHWX-ray3.60F26-513[»]
4MMQX-ray3.25A26-107[»]
B137-513[»]
4MMRX-ray3.10A26-107[»]
B137-513[»]
4MMSX-ray2.40A/C/E26-107[»]
B/D/F137-513[»]
4MMTX-ray3.05A26-107[»]
B137-513[»]
4MMUX-ray3.00A26-107[»]
B137-513[»]
4MMVX-ray2.81A26-107[»]
B137-513[»]
ProteinModelPortaliP03420.
SMRiP03420. Positions 158-207, 477-516.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

DIPiDIP-48772N.

Protein family/group databases

TCDBi1.G.2.1.3. the viral pore-forming membrane fusion protein-2 (vmfp2) family.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Miscellaneous databases

EvolutionaryTraceiP03420.

Family and domain databases

InterProiIPR000776. Fusion_F0_Paramyxovir.
[Graphical view]
PfamiPF00523. Fusion_gly. 1 hit.
[Graphical view]
ProtoNetiSearch...

Publicationsi

  1. "Nucleotide sequence of the gene encoding the fusion (F) glycoprotein of human respiratory syncytial virus."
    Collins P.L., Huang Y.T., Wertz G.W.
    Proc. Natl. Acad. Sci. U.S.A. 81:7683-7687(1984) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC RNA].
  2. "Nucleotide sequence analysis of the respiratory syncytial virus subgroup A cold-passaged (cp) temperature sensitive (ts) cpts-248/404 live attenuated virus vaccine candidate."
    Firestone C.Y., Whitehead S.S., Collins P.L., Murphy B.R., Crowe J.E. Jr.
    Virology 225:419-422(1996) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC RNA].
    Strain: Cold-passage attenuated.
  3. "Acquisition of the ts phenotype by a chemically mutagenized cold-passaged human respiratory syncytial virus vaccine candidate results from the acquisition of a single mutation in the polymerase (L) gene."
    Crowe J.E. Jr., Firestone C.Y., Whitehead S.S., Collins P.L., Murphy B.R.
    Virus Genes 13:269-273(1996) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC RNA].
    Strain: Cold-passage attenuated.
  4. "A cold-passaged, attenuated strain of human respiratory syncytial virus contains mutations in the F and L genes."
    Connors M., Crowe J.E. Jr., Firestone C.Y., Murphy B.R., Collins P.L.
    Virology 208:478-484(1995) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC RNA].
    Strain: Cold-passage attenuated.
  5. "Recombinant respiratory syncytial virus (RSV) bearing a set of mutations from cold-passaged RSV is attenuated in chimpanzees."
    Whitehead S.S., Juhasz K., Firestone C.Y., Collins P.L., Murphy B.R.
    J. Virol. 72:4467-4471(1998) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC RNA].
    Strain: Cold-passage attenuated.
  6. "Fatty acid acylation of the fusion glycoprotein of human respiratory syncytial virus."
    Arumugham R.G., Seid R.C. Jr., Doyle S., Hildreth S.W., Paradisio P.R.
    J. Biol. Chem. 264:10339-10342(1989) [PubMed] [Europe PMC] [Abstract]
    Cited for: PALMITOYLATION AT CYS-550.
  7. "RhoA interacts with the fusion glycoprotein of respiratory syncytial virus and facilitates virus-induced syncytium formation."
    Pastey M.K., Crowe J.E. Jr., Graham B.S.
    J. Virol. 73:7262-7270(1999) [PubMed] [Europe PMC] [Abstract]
    Cited for: INTERACTION WITH HOST RHOA.
  8. "The fusion glycoprotein of human respiratory syncytial virus facilitates virus attachment and infectivity via an interaction with cellular heparan sulfate."
    Feldman S.A., Audet S., Beeler J.A.
    J. Virol. 74:6442-6447(2000) [PubMed] [Europe PMC] [Abstract]
    Cited for: INTERACTION WITH HEPARAN SULFATE.
  9. "The core of the respiratory syncytial virus fusion protein is a trimeric coiled coil."
    Matthews J.M., Young T.F., Tucker S.P., Mackay J.P.
    J. Virol. 74:5911-5920(2000) [PubMed] [Europe PMC] [Abstract]
    Cited for: HOMOTRIMERIZATION.
  10. "Furin cleavage of the respiratory syncytial virus fusion protein is not a requirement for its transport to the surface of virus-infected cells."
    Sugrue R.J., Brown C., Brown G., Aitken J., McL Rixon H.W.
    J. Gen. Virol. 82:1375-1386(2001) [PubMed] [Europe PMC] [Abstract]
    Cited for: CLEAVAGE BY HOST FURIN.
  11. "Cleavage of the human respiratory syncytial virus fusion protein at two distinct sites is required for activation of membrane fusion."
    Gonzalez-Reyes L., Ruiz-Argueello M.B., Garcia-Barreno B., Calder L., Lopez J.A., Albar J.P., Skehel J.J., Wiley D.C., Melero J.A.
    Proc. Natl. Acad. Sci. U.S.A. 98:9859-9864(2001) [PubMed] [Europe PMC] [Abstract]
    Cited for: CLEAVAGE.
  12. "Respiratory syncytial virus (RSV) fusion protein subunit F2, not attachment protein G, determines the specificity of RSV infection."
    Schlender J., Zimmer G., Herrler G., Conzelmann K.K.
    J. Virol. 77:4609-4616(2003) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION IN HOST CELL SPECIFICITY.
  13. "The transmembrane domain of the respiratory syncytial virus F protein is an orientation-independent apical plasma membrane sorting sequence."
    Brock S.C., Heck J.M., McGraw P.A., Crowe J.E. Jr.
    J. Virol. 79:12528-12535(2005) [PubMed] [Europe PMC] [Abstract]
    Cited for: SUBCELLULAR LOCATION.
  14. "The fusion protein of respiratory syncytial virus triggers p53-dependent apoptosis."
    Eckardt-Michel J., Lorek M., Baxmann D., Grunwald T., Keil G.M., Zimmer G.
    J. Virol. 82:3236-3249(2008) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION IN APOPTOSIS.
  15. "The RSV F and G glycoproteins interact to form a complex on the surface of infected cells."
    Low K.W., Tan T., Ng K., Tan B.H., Sugrue R.J.
    Biochem. Biophys. Res. Commun. 366:308-313(2008) [PubMed] [Europe PMC] [Abstract]
    Cited for: INTERACTION WITH GLYCOPROTEIN G.
  16. "Host cell entry of respiratory syncytial virus involves macropinocytosis followed by proteolytic activation of the F protein."
    Krzyzaniak M.A., Zumstein M.T., Gerez J.A., Picotti P., Helenius A.
    PLoS Pathog. 9:E1003309-E1003309(2013) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION.
  17. "Structural basis of respiratory syncytial virus neutralization by motavizumab."
    McLellan J.S., Chen M., Kim A., Yang Y., Graham B.S., Kwong P.D.
    Nat. Struct. Mol. Biol. 17:248-250(2010) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (2.75 ANGSTROMS) OF 254-277.
  18. "Binding of a potent small-molecule inhibitor of six-helix bundle formation requires interactions with both heptad-repeats of the RSV fusion protein."
    Roymans D., De Bondt H.L., Arnoult E., Geluykens P., Gevers T., Van Ginderen M., Verheyen N., Kim H., Willebrords R., Bonfanti J.F., Bruinzeel W., Cummings M.D., van Vlijmen H., Andries K.
    Proc. Natl. Acad. Sci. U.S.A. 107:308-313(2010) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (1.47 ANGSTROMS) OF 159-209 OF 482-520.
  19. "Structure of respiratory syncytial virus fusion glycoprotein in the postfusion conformation reveals preservation of neutralizing epitopes."
    McLellan J.S., Yang Y., Graham B.S., Kwong P.D.
    J. Virol. 85:7788-7796(2011) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (2.82 ANGSTROMS) OF 26-109 OF 147-513.
  20. "Structural basis for immunization with postfusion respiratory syncytial virus fusion F glycoprotein (RSV F) to elicit high neutralizing antibody titers."
    Swanson K.A., Settembre E.C., Shaw C.A., Dey A.K., Rappuoli R., Mandl C.W., Dormitzer P.R., Carfi A.
    Proc. Natl. Acad. Sci. U.S.A. 108:9619-9624(2011) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (3.20 ANGSTROMS) OF 1-524.
  21. "Structure of RSV fusion glycoprotein trimer bound to a prefusion-specific neutralizing antibody."
    McLellan J.S., Chen M., Leung S., Graepel K.W., Du X., Yang Y., Zhou T., Baxa U., Yasuda E., Beaumont T., Kumar A., Modjarrad K., Zheng Z., Zhao M., Xia N., Kwong P.D., Graham B.S.
    Science 340:1113-1117(2013) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (3.60 ANGSTROMS) OF 26-513.
  22. Cited for: X-RAY CRYSTALLOGRAPHY (2.40 ANGSTROMS) OF 26-107 OF 137-513.

Entry informationi

Entry nameiFUS_HRSVA
AccessioniPrimary (citable) accession number: P03420
Secondary accession number(s): P88811
Entry historyi
Integrated into UniProtKB/Swiss-Prot: July 21, 1986
Last sequence update: July 21, 1986
Last modified: June 24, 2015
This is version 97 of the entry and version 1 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programViral Protein Annotation Program

Miscellaneousi

Keywords - Technical termi

3D-structure, Complete proteome

Documents

  1. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  2. SIMILARITY comments
    Index of protein domains and families

External Data

Dasty 3

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 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.