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Protein

Integrin alpha-2

Gene

ITGA2

Organism
Homo sapiens (Human)
Status
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli

Functioni

Integrin alpha-2/beta-1 is a receptor for laminin, collagen, collagen C-propeptides, fibronectin and E-cadherin. It recognizes the proline-hydroxylated sequence G-F-P-G-E-R in collagen. It is responsible for adhesion of platelets and other cells to collagens, modulation of collagen and collagenase gene expression, force generation and organization of newly synthesized extracellular matrix.
(Microbial infection) Integrin ITGA2:ITGB1 acts as a receptor for human rotavirus A (PubMed:12941907). Integrin ITGA2:ITGB1 acts as a receptor for human echoviruses 1 and 8 (PubMed:8411387).2 Publications

Regions

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Calcium bindingi499 – 507Sequence analysis9
Calcium bindingi563 – 571Sequence analysis9
Calcium bindingi627 – 635Sequence analysis9

GO - Molecular functioni

  • collagen binding Source: UniProtKB
  • collagen binding involved in cell-matrix adhesion Source: UniProtKB
  • collagen receptor activity Source: UniProtKB
  • metal ion binding Source: UniProtKB-KW
  • protein complex binding Source: UniProtKB
  • virus receptor activity Source: UniProtKB-KW

GO - Biological processi

Complete GO annotation...

Keywords - Molecular functioni

Host cell receptor for virus entry, Integrin, Receptor

Keywords - Biological processi

Cell adhesion, Host-virus interaction

Keywords - Ligandi

Calcium, Magnesium, Metal-binding

Enzyme and pathway databases

BioCyciZFISH:ENSG00000164171-MONOMER.
ReactomeiR-HSA-216083. Integrin cell surface interactions.
R-HSA-3000157. Laminin interactions.
R-HSA-3000170. Syndecan interactions.
R-HSA-3000178. ECM proteoglycans.
R-HSA-447041. CHL1 interactions.
R-HSA-75892. Platelet Adhesion to exposed collagen.
R-HSA-8874081. MET activates PTK2 signaling.
SignaLinkiP17301.
SIGNORiP17301.

Names & Taxonomyi

Protein namesi
Recommended name:
Integrin alpha-2
Alternative name(s):
CD49 antigen-like family member B
Collagen receptor
Platelet membrane glycoprotein Ia
Short name:
GPIa
VLA-2 subunit alpha
CD_antigen: CD49b
Gene namesi
Name:ITGA2
Synonyms:CD49B
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
Proteomesi
  • UP000005640 Componenti: Chromosome 5

Organism-specific databases

HGNCiHGNC:6137. ITGA2.

Subcellular locationi

Topology

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Topological domaini30 – 1132ExtracellularSequence analysisAdd BLAST1103
Transmembranei1133 – 1154HelicalSequence analysisAdd BLAST22
Topological domaini1155 – 1181CytoplasmicSequence analysisAdd BLAST27

GO - Cellular componenti

  • axon terminus Source: Ensembl
  • basal part of cell Source: Ensembl
  • cell surface Source: UniProtKB
  • external side of plasma membrane Source: Ensembl
  • focal adhesion Source: UniProtKB
  • integrin alpha2-beta1 complex Source: UniProtKB
  • integrin complex Source: ProtInc
  • nucleus Source: Ensembl
  • perinuclear region of cytoplasm Source: Ensembl
  • plasma membrane Source: BHF-UCL
Complete GO annotation...

Keywords - Cellular componenti

Membrane

Pathology & Biotechi

Mutagenesis

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Mutagenesisi1159F → A: No significant reduction of RAB21-binding by co-immunoprecipitation assay; when associated with A-1160 and A-1162. 1 Publication1
Mutagenesisi1160K → A: No effect on RAB21-binding. Significant reduction of RAB21-binding; when associated with A-1161. Shows defective cytokinesis on collagen, but not on fibronectin; when associated with A-1161. 2 Publications1
Mutagenesisi1161R → A: Significant reduction of RAB21-binding; when associated with A-1160. Shows defective cytokinesis on collagen, but not on fibronectin; when associated with A-1160. 2 Publications1
Mutagenesisi1162K → A: No significant reduction of RAB21-binding by co-immunoprecipitation assay; when associated with A-1159 and A-1160. 2 Publications1
Mutagenesisi1162K → P: Markedly weakens RAB21-binding. Shows defective cytokinesis on collagen, but not on fibronectin. 2 Publications1
Mutagenesisi1164E → A: Significant reduction of RAB21-binding; when associated with A-1160; A-1161 and A-1165. 1 Publication1
Mutagenesisi1165K → A: Significant reduction of RAB21-binding; when associated with A-1160; A-1161 and A-1164. 1 Publication1

Organism-specific databases

DisGeNETi3673.
MalaCardsiITGA2.
MIMi192974. gene+phenotype.
Orphaneti853. Fetal and neonatal alloimmune thrombocytopenia.
PharmGKBiPA204.

Chemistry databases

ChEMBLiCHEMBL4998.

Polymorphism and mutation databases

BioMutaiITGA2.
DMDMi124942.

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Signal peptidei1 – 291 PublicationAdd BLAST29
ChainiPRO_000001623330 – 1181Integrin alpha-2Add BLAST1152

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Disulfide bondi83 ↔ 92By similarity
Glycosylationi105N-linked (GlcNAc...)Sequence analysis1
Glycosylationi112N-linked (GlcNAc...)Sequence analysis1
Glycosylationi343N-linked (GlcNAc...)3 Publications1
Glycosylationi432N-linked (GlcNAc...)Sequence analysis1
Glycosylationi460N-linked (GlcNAc...)Sequence analysis1
Glycosylationi475N-linked (GlcNAc...)Sequence analysis1
Disulfide bondi680 ↔ 737By similarity
Glycosylationi699N-linked (GlcNAc...)Sequence analysis1
Disulfide bondi789 ↔ 795By similarity
Disulfide bondi865 ↔ 876By similarity
Disulfide bondi1019 ↔ 1050By similarity
Disulfide bondi1055 ↔ 1060By similarity
Glycosylationi1057N-linked (GlcNAc...)Sequence analysis1
Glycosylationi1074N-linked (GlcNAc...)Sequence analysis1
Glycosylationi1081N-linked (GlcNAc...)Sequence analysis1

Keywords - PTMi

Disulfide bond, Glycoprotein

Proteomic databases

EPDiP17301.
MaxQBiP17301.
PaxDbiP17301.
PeptideAtlasiP17301.
PRIDEiP17301.

PTM databases

iPTMnetiP17301.
PhosphoSitePlusiP17301.
SwissPalmiP17301.

Expressioni

Gene expression databases

BgeeiENSG00000164171.
CleanExiHS_ITGA2.
ExpressionAtlasiP17301. baseline and differential.
GenevisibleiP17301. HS.

Organism-specific databases

HPAiCAB017690.
HPA060991.
HPA063556.

Interactioni

Subunit structurei

Heterodimer of an alpha and a beta subunit. Alpha-2 associates with beta-1. Interacts with HPS5 and RAB21.1 Publication
(Microbial infection) Integrin ITGA2:ITGB1 interacts (via ITAG2 I-domain) with rotavirus A VP4 protein.1 Publication
(Microbial infection) Integrin ITGA2:ITGB1 interacts with human echoviruses 1 and 8 capsid proteins.1 Publication

Binary interactionsi

WithEntry#Exp.IntActNotes
ITGB1P055563EBI-702960,EBI-703066
KDRP359682EBI-702960,EBI-1005487
Rab21P352827EBI-702960,EBI-1993555From a different organism.
SHARPINQ9H0F65EBI-702960,EBI-3942966

GO - Molecular functioni

  • collagen binding Source: UniProtKB
  • collagen binding involved in cell-matrix adhesion Source: UniProtKB
  • protein complex binding Source: UniProtKB

Protein-protein interaction databases

BioGridi109880. 26 interactors.
DIPiDIP-67N.
IntActiP17301. 18 interactors.
MINTiMINT-5004079.
STRINGi9606.ENSP00000296585.

Chemistry databases

BindingDBiP17301.

Structurei

Secondary structure

11181
Legend: HelixTurnBeta strandPDB Structure known for this area
Show more details
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Beta strandi173 – 180Combined sources8
Helixi188 – 200Combined sources13
Beta strandi208 – 224Combined sources17
Turni226 – 228Combined sources3
Helixi232 – 241Combined sources10
Helixi252 – 262Combined sources11
Helixi266 – 268Combined sources3
Beta strandi274 – 284Combined sources11
Helixi289 – 291Combined sources3
Helixi292 – 301Combined sources10
Beta strandi304 – 311Combined sources8
Helixi313 – 317Combined sources5
Helixi323 – 332Combined sources10
Helixi337 – 340Combined sources4
Beta strandi341 – 347Combined sources7
Helixi348 – 353Combined sources6
Helixi354 – 362Combined sources9

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
1AOXX-ray2.10A/B169-367[»]
1DZIX-ray2.10A172-355[»]
1PQBmodel-A/B169-366[»]
1V7PX-ray1.90C167-366[»]
4BJ3X-ray3.04A/B171-368[»]
ProteinModelPortaliP17301.
SMRiP17301.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiP17301.

Family & Domainsi

Domains and Repeats

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Repeati34 – 92FG-GAP 1PROSITE-ProRule annotationAdd BLAST59
Repeati101 – 161FG-GAP 2PROSITE-ProRule annotationAdd BLAST61
Domaini188 – 365VWFAPROSITE-ProRule annotationAdd BLAST178
Repeati366 – 420FG-GAP 3PROSITE-ProRule annotationAdd BLAST55
Repeati423 – 475FG-GAP 4PROSITE-ProRule annotationAdd BLAST53
Repeati477 – 539FG-GAP 5PROSITE-ProRule annotationAdd BLAST63
Repeati540 – 598FG-GAP 6PROSITE-ProRule annotationAdd BLAST59
Repeati602 – 664FG-GAP 7PROSITE-ProRule annotationAdd BLAST63

Region

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Regioni1155 – 1161Interaction with HPS57

Motif

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Motifi1157 – 1161GFFKR motif5

Domaini

The integrin I-domain (insert) is a VWFA domain. Integrins with I-domains do not undergo protease cleavage.

Sequence similaritiesi

Belongs to the integrin alpha chain family.Curated
Contains 7 FG-GAP repeats.PROSITE-ProRule annotation
Contains 1 VWFA domain.PROSITE-ProRule annotation

Keywords - Domaini

Repeat, Signal, Transmembrane, Transmembrane helix

Phylogenomic databases

eggNOGiENOG410IPB9. Eukaryota.
ENOG4110534. LUCA.
HOGENOMiHOG000059610.
HOVERGENiHBG006185.
InParanoidiP17301.
KOiK06481.
OrthoDBiEOG091G00TK.
PhylomeDBiP17301.
TreeFamiTF105391.

Family and domain databases

InterProiIPR013517. FG-GAP.
IPR013519. Int_alpha_beta-p.
IPR000413. Integrin_alpha.
IPR013649. Integrin_alpha-2.
IPR018184. Integrin_alpha_C_CS.
IPR032695. Integrin_dom.
IPR002035. VWF_A.
[Graphical view]
PfamiPF01839. FG-GAP. 2 hits.
PF08441. Integrin_alpha2. 1 hit.
PF00092. VWA. 1 hit.
[Graphical view]
PRINTSiPR01185. INTEGRINA.
SMARTiSM00191. Int_alpha. 5 hits.
SM00327. VWA. 1 hit.
[Graphical view]
SUPFAMiSSF53300. SSF53300. 1 hit.
SSF69179. SSF69179. 3 hits.
PROSITEiPS51470. FG_GAP. 7 hits.
PS00242. INTEGRIN_ALPHA. 1 hit.
PS50234. VWFA. 1 hit.
[Graphical view]

Sequencei

Sequence statusi: Complete.

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

P17301-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MGPERTGAAP LPLLLVLALS QGILNCCLAY NVGLPEAKIF SGPSSEQFGY
60 70 80 90 100
AVQQFINPKG NWLLVGSPWS GFPENRMGDV YKCPVDLSTA TCEKLNLQTS
110 120 130 140 150
TSIPNVTEMK TNMSLGLILT RNMGTGGFLT CGPLWAQQCG NQYYTTGVCS
160 170 180 190 200
DISPDFQLSA SFSPATQPCP SLIDVVVVCD ESNSIYPWDA VKNFLEKFVQ
210 220 230 240 250
GLDIGPTKTQ VGLIQYANNP RVVFNLNTYK TKEEMIVATS QTSQYGGDLT
260 270 280 290 300
NTFGAIQYAR KYAYSAASGG RRSATKVMVV VTDGESHDGS MLKAVIDQCN
310 320 330 340 350
HDNILRFGIA VLGYLNRNAL DTKNLIKEIK AIASIPTERY FFNVSDEAAL
360 370 380 390 400
LEKAGTLGEQ IFSIEGTVQG GDNFQMEMSQ VGFSADYSSQ NDILMLGAVG
410 420 430 440 450
AFGWSGTIVQ KTSHGHLIFP KQAFDQILQD RNHSSYLGYS VAAISTGEST
460 470 480 490 500
HFVAGAPRAN YTGQIVLYSV NENGNITVIQ AHRGDQIGSY FGSVLCSVDV
510 520 530 540 550
DKDTITDVLL VGAPMYMSDL KKEEGRVYLF TIKKGILGQH QFLEGPEGIE
560 570 580 590 600
NTRFGSAIAA LSDINMDGFN DVIVGSPLEN QNSGAVYIYN GHQGTIRTKY
610 620 630 640 650
SQKILGSDGA FRSHLQYFGR SLDGYGDLNG DSITDVSIGA FGQVVQLWSQ
660 670 680 690 700
SIADVAIEAS FTPEKITLVN KNAQIILKLC FSAKFRPTKQ NNQVAIVYNI
710 720 730 740 750
TLDADGFSSR VTSRGLFKEN NERCLQKNMV VNQAQSCPEH IIYIQEPSDV
760 770 780 790 800
VNSLDLRVDI SLENPGTSPA LEAYSETAKV FSIPFHKDCG EDGLCISDLV
810 820 830 840 850
LDVRQIPAAQ EQPFIVSNQN KRLTFSVTLK NKRESAYNTG IVVDFSENLF
860 870 880 890 900
FASFSLPVDG TEVTCQVAAS QKSVACDVGY PALKREQQVT FTINFDFNLQ
910 920 930 940 950
NLQNQASLSF QALSESQEEN KADNLVNLKI PLLYDAEIHL TRSTNINFYE
960 970 980 990 1000
ISSDGNVPSI VHSFEDVGPK FIFSLKVTTG SVPVSMATVI IHIPQYTKEK
1010 1020 1030 1040 1050
NPLMYLTGVQ TDKAGDISCN ADINPLKIGQ TSSSVSFKSE NFRHTKELNC
1060 1070 1080 1090 1100
RTASCSNVTC WLKDVHMKGE YFVNVTTRIW NGTFASSTFQ TVQLTAAAEI
1110 1120 1130 1140 1150
NTYNPEIYVI EDNTVTIPLM IMKPDEKAEV PTGVIIGSII AGILLLLALV
1160 1170 1180
AILWKLGFFK RKYEKMTKNP DEIDETTELS S
Length:1,181
Mass (Da):129,295
Last modified:August 1, 1990 - v1
Checksum:i7E1B7ED968A94070
GO

Experimental Info

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sequence conflicti17L → V in AAA16619 (PubMed:15372022).Curated1

Polymorphismi

Position 534 is associated with platelet-specific alloantigen HPA-5 (Br). HPA-5A/Br(a) has Lys-534 and HPA-5B/Br(b) has Glu-534. HPA-5B is involved in neonatal alloimmune thrombocytopenia (NAIT or NATP). The Lys-534-Glu polymorphism may play a role in coronary artery disease (CAD).1 Publication

Natural variant

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Natural variantiVAR_076939532I → L.1 Publication1
Natural variantiVAR_003977534K → E in alloantigen HPA-5B. 3 PublicationsCorresponds to variant rs1801106dbSNPEnsembl.1
Natural variantiVAR_029146691N → K.1 PublicationCorresponds to variant rs3212557dbSNPEnsembl.1
Natural variantiVAR_021855927N → S.Corresponds to variant rs2287870dbSNPEnsembl.1
Natural variantiVAR_0200361127K → Q.1 PublicationCorresponds to variant rs3212645dbSNPEnsembl.1

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
X17033 mRNA. Translation: CAA34894.1.
AF512556 Genomic DNA. Translation: AAM34795.1.
L24121 Genomic DNA. Translation: AAA16619.2.
CCDSiCCDS3957.1.
PIRiA33998.
RefSeqiNP_002194.2. NM_002203.3.
UniGeneiHs.482077.

Genome annotation databases

EnsembliENST00000296585; ENSP00000296585; ENSG00000164171.
GeneIDi3673.
KEGGihsa:3673.
UCSCiuc003joy.3. human.

Keywords - Coding sequence diversityi

Polymorphism

Cross-referencesi

Web resourcesi

SeattleSNPs

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
X17033 mRNA. Translation: CAA34894.1.
AF512556 Genomic DNA. Translation: AAM34795.1.
L24121 Genomic DNA. Translation: AAA16619.2.
CCDSiCCDS3957.1.
PIRiA33998.
RefSeqiNP_002194.2. NM_002203.3.
UniGeneiHs.482077.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
1AOXX-ray2.10A/B169-367[»]
1DZIX-ray2.10A172-355[»]
1PQBmodel-A/B169-366[»]
1V7PX-ray1.90C167-366[»]
4BJ3X-ray3.04A/B171-368[»]
ProteinModelPortaliP17301.
SMRiP17301.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi109880. 26 interactors.
DIPiDIP-67N.
IntActiP17301. 18 interactors.
MINTiMINT-5004079.
STRINGi9606.ENSP00000296585.

Chemistry databases

BindingDBiP17301.
ChEMBLiCHEMBL4998.

PTM databases

iPTMnetiP17301.
PhosphoSitePlusiP17301.
SwissPalmiP17301.

Polymorphism and mutation databases

BioMutaiITGA2.
DMDMi124942.

Proteomic databases

EPDiP17301.
MaxQBiP17301.
PaxDbiP17301.
PeptideAtlasiP17301.
PRIDEiP17301.

Protocols and materials databases

DNASUi3673.
Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000296585; ENSP00000296585; ENSG00000164171.
GeneIDi3673.
KEGGihsa:3673.
UCSCiuc003joy.3. human.

Organism-specific databases

CTDi3673.
DisGeNETi3673.
GeneCardsiITGA2.
H-InvDBHIX0032121.
HGNCiHGNC:6137. ITGA2.
HPAiCAB017690.
HPA060991.
HPA063556.
MalaCardsiITGA2.
MIMi192974. gene+phenotype.
neXtProtiNX_P17301.
Orphaneti853. Fetal and neonatal alloimmune thrombocytopenia.
PharmGKBiPA204.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiENOG410IPB9. Eukaryota.
ENOG4110534. LUCA.
HOGENOMiHOG000059610.
HOVERGENiHBG006185.
InParanoidiP17301.
KOiK06481.
OrthoDBiEOG091G00TK.
PhylomeDBiP17301.
TreeFamiTF105391.

Enzyme and pathway databases

BioCyciZFISH:ENSG00000164171-MONOMER.
ReactomeiR-HSA-216083. Integrin cell surface interactions.
R-HSA-3000157. Laminin interactions.
R-HSA-3000170. Syndecan interactions.
R-HSA-3000178. ECM proteoglycans.
R-HSA-447041. CHL1 interactions.
R-HSA-75892. Platelet Adhesion to exposed collagen.
R-HSA-8874081. MET activates PTK2 signaling.
SignaLinkiP17301.
SIGNORiP17301.

Miscellaneous databases

ChiTaRSiITGA2. human.
EvolutionaryTraceiP17301.
GeneWikiiCD49b.
GenomeRNAii3673.
PROiP17301.
SOURCEiSearch...

Gene expression databases

BgeeiENSG00000164171.
CleanExiHS_ITGA2.
ExpressionAtlasiP17301. baseline and differential.
GenevisibleiP17301. HS.

Family and domain databases

InterProiIPR013517. FG-GAP.
IPR013519. Int_alpha_beta-p.
IPR000413. Integrin_alpha.
IPR013649. Integrin_alpha-2.
IPR018184. Integrin_alpha_C_CS.
IPR032695. Integrin_dom.
IPR002035. VWF_A.
[Graphical view]
PfamiPF01839. FG-GAP. 2 hits.
PF08441. Integrin_alpha2. 1 hit.
PF00092. VWA. 1 hit.
[Graphical view]
PRINTSiPR01185. INTEGRINA.
SMARTiSM00191. Int_alpha. 5 hits.
SM00327. VWA. 1 hit.
[Graphical view]
SUPFAMiSSF53300. SSF53300. 1 hit.
SSF69179. SSF69179. 3 hits.
PROSITEiPS51470. FG_GAP. 7 hits.
PS00242. INTEGRIN_ALPHA. 1 hit.
PS50234. VWFA. 1 hit.
[Graphical view]
ProtoNetiSearch...

Entry informationi

Entry nameiITA2_HUMAN
AccessioniPrimary (citable) accession number: P17301
Secondary accession number(s): Q14595
Entry historyi
Integrated into UniProtKB/Swiss-Prot: August 1, 1990
Last sequence update: August 1, 1990
Last modified: November 30, 2016
This is version 194 of the entry and version 1 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programChordata Protein Annotation Program
DisclaimerAny medical or genetic information present in this entry is provided for research, educational and informational purposes only. It is not in any way intended to be used as a substitute for professional medical advice, diagnosis, treatment or care.

Miscellaneousi

Keywords - Technical termi

3D-structure, Complete proteome, Direct protein sequencing, Reference proteome

Documents

  1. Human cell differentiation molecules
    CD nomenclature of surface proteins of human leucocytes and list of entries
  2. Human chromosome 5
    Human chromosome 5: entries, gene names and cross-references to MIM
  3. Human entries with polymorphisms or disease mutations
    List of human entries with polymorphisms or disease mutations
  4. Human polymorphisms and disease mutations
    Index of human polymorphisms and disease mutations
  5. MIM cross-references
    Online Mendelian Inheritance in Man (MIM) cross-references in UniProtKB/Swiss-Prot
  6. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  7. SIMILARITY comments
    Index of protein domains and families

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.