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Protein

Flap endonuclease 1

Gene

FEN1

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

Functioni

Structure-specific nuclease with 5'-flap endonuclease and 5'-3' exonuclease activities involved in DNA replication and repair. During DNA replication, cleaves the 5'-overhanging flap structure that is generated by displacement synthesis when DNA polymerase encounters the 5'-end of a downstream Okazaki fragment. It enters the flap from the 5'-end and then tracks to cleave the flap base, leaving a nick for ligation. Also involved in the long patch base excision repair (LP-BER) pathway, by cleaving within the apurinic/apyrimidinic (AP) site-terminated flap. Acts as a genome stabilization factor that prevents flaps from equilibrating into structurs that lead to duplications and deletions. Also possesses 5'-3' exonuclease activity on nicked or gapped double-stranded DNA, and exhibits RNase H activity. Also involved in replication and repair of rDNA and in repairing mitochondrial DNA.UniRule annotation6 Publications

Cofactori

Mg2+Note: Binds 2 magnesium ions per subunit. They probably participate in the reaction catalyzed by the enzyme. May bind an additional third magnesium ion after substrate binding.

Sites

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Metal bindingi34Magnesium 11
Binding sitei47DNA substrate1
Binding sitei70DNA substrate1
Metal bindingi86Magnesium 11
Metal bindingi158Magnesium 11
Binding sitei158DNA substrate1
Metal bindingi160Magnesium 11
Metal bindingi179Magnesium 21
Metal bindingi181Magnesium 21
Binding sitei231DNA substrate1
Metal bindingi233Magnesium 21
Binding sitei233DNA substrate1

GO - Molecular functioni

  • 5'-3' exonuclease activity Source: UniProtKB
  • 5'-flap endonuclease activity Source: UniProtKB
  • damaged DNA binding Source: ProtInc
  • DNA binding Source: UniProtKB
  • double-stranded DNA binding Source: ProtInc
  • double-stranded DNA exodeoxyribonuclease activity Source: ProtInc
  • endonuclease activity Source: ProtInc
  • exonuclease activity Source: ProtInc
  • flap endonuclease activity Source: UniProtKB
  • magnesium ion binding Source: UniProtKB-HAMAP
  • RNA-DNA hybrid ribonuclease activity Source: UniProtKB

GO - Biological processi

  • base-excision repair Source: UniProtKB-HAMAP
  • DNA repair Source: ProtInc
  • DNA replication Source: ProtInc
  • DNA replication, removal of RNA primer Source: UniProtKB
  • double-strand break repair Source: ProtInc
  • double-strand break repair via homologous recombination Source: Reactome
  • memory Source: Ensembl
  • nucleic acid phosphodiester bond hydrolysis Source: UniProtKB
  • positive regulation of sister chromatid cohesion Source: UniProtKB
  • telomere maintenance via recombination Source: Reactome
  • UV protection Source: ProtInc
Complete GO annotation...

Keywords - Molecular functioni

Endonuclease, Exonuclease, Hydrolase, Nuclease

Keywords - Biological processi

DNA damage, DNA repair, DNA replication

Keywords - Ligandi

Magnesium, Metal-binding

Enzyme and pathway databases

BioCyciZFISH:HS09774-MONOMER.
ReactomeiR-HSA-110362. POLB-Dependent Long Patch Base Excision Repair.
R-HSA-162594. Early Phase of HIV Life Cycle.
R-HSA-174437. Removal of the Flap Intermediate from the C-strand.
R-HSA-5651801. PCNA-Dependent Long Patch Base Excision Repair.
R-HSA-5685939. HDR through MMEJ (alt-NHEJ).
R-HSA-69166. Removal of the Flap Intermediate.
SignaLinkiP39748.
SIGNORiP39748.

Names & Taxonomyi

Protein namesi
Recommended name:
Flap endonuclease 1UniRule annotation (EC:3.1.-.-UniRule annotation)
Short name:
FEN-1UniRule annotation
Alternative name(s):
DNase IV
Flap structure-specific endonuclease 1UniRule annotation
Maturation factor 1
Short name:
MF1
Short name:
hFEN-1
Gene namesi
Name:FEN1UniRule annotation
Synonyms:RAD2
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
Proteomesi
  • UP000005640 Componenti: Chromosome 11

Organism-specific databases

HGNCiHGNC:3650. FEN1.

Subcellular locationi

Isoform 1 :
Isoform FENMIT :
  • Mitochondrion UniRule annotation1 Publication

GO - Cellular componenti

  • membrane Source: UniProtKB
  • mitochondrion Source: UniProtKB
  • nuclear chromosome, telomeric region Source: BHF-UCL
  • nucleolus Source: HPA
  • nucleoplasm Source: Reactome
  • nucleus Source: UniProtKB
  • plasma membrane Source: HPA
  • protein complex Source: MGI
Complete GO annotation...

Keywords - Cellular componenti

Mitochondrion, Nucleus

Pathology & Biotechi

Mutagenesis

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Mutagenesisi29R → A: No significant effect on exonuclease activity or flap endonuclease activity. 1 Publication1
Mutagenesisi34D → A: Loss of flap endonuclease activity but substrate binding activity is retained. 1 Publication1
Mutagenesisi47R → A: Significantly reduced exonuclease activity and reduced substrate binding. The positions of the cleavage sites are also shifted. 1 Publication1
Mutagenesisi70R → A: Loss of exonuclease activity and reduced endonuclease activity. Reduced substrate binding. 1 Publication1
Mutagenesisi73R → A: No significant effect on exonuclease activity or flap endonuclease activity. 1 Publication1
Mutagenesisi80K → A: No significant effect on exonuclease activity or flap endonuclease activity. 1 Publication1
Mutagenesisi86D → A: Loss of flap endonuclease activity but substrate binding activity is retained. 1 Publication1
Mutagenesisi103R → A: No effect on flap endonuclease activity or substrate binding. 1 Publication1
Mutagenesisi158E → A: Loss of flap endonuclease activity and substrate binding. 1 Publication1
Mutagenesisi179D → A: No effect on flap endonuclease activity or substrate binding. 1 Publication1
Mutagenesisi181D → A: Loss of flap endonuclease activity but substrate binding activity is retained. 1 Publication1
Mutagenesisi187S → A: Fails to translocate from nucleoli to the nuclear plasma. 1 Publication1
Mutagenesisi187S → D: Diminishes nucleolar localization. 1 Publication1
Mutagenesisi192R → K: Impairs ability to localize to sites of DNA replication or repair. 1 Publication1
Mutagenesisi231G → A: Loss of flap endonuclease activity and substrate binding. 1 Publication1
Mutagenesisi233D → A: Loss of flap endonuclease activity and substrate binding. 1 Publication1

Organism-specific databases

DisGeNETi2237.
OpenTargetsiENSG00000168496.
PharmGKBiPA28090.

Chemistry databases

ChEMBLiCHEMBL5027.

Polymorphism and mutation databases

BioMutaiFEN1.
DMDMi729475.

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
ChainiPRO_00001540691 – 380Flap endonuclease 1Add BLAST380

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Modified residuei19Symmetric dimethylarginine; by PRMT5UniRule annotation1 Publication1
Modified residuei80N6-acetyllysineCombined sources1
Modified residuei100Symmetric dimethylarginine; by PRMT5UniRule annotation1 Publication1
Modified residuei104Symmetric dimethylarginine; by PRMT5UniRule annotation1 Publication1
Modified residuei187Phosphoserine; by CDK2UniRule annotation1 Publication1
Modified residuei192Symmetric dimethylarginine; by PRMT5UniRule annotation1 Publication1
Modified residuei197PhosphoserineCombined sources1
Modified residuei255PhosphoserineCombined sources1
Modified residuei293PhosphoserineCombined sources1
Modified residuei335PhosphoserineCombined sources1
Modified residuei336PhosphothreonineCombined sources1
Modified residuei354N6-acetyllysineUniRule annotation1 Publication1
Modified residuei364PhosphothreonineCombined sources1
Modified residuei375N6-acetyllysineUniRule annotationCombined sources1 Publication1
Modified residuei377N6-acetyllysineUniRule annotation1 Publication1
Modified residuei380N6-acetyllysineUniRule annotation1 Publication1

Post-translational modificationi

Acetylated by EP300. Acetylation inhibits both endonuclease and exonuclease activity. Acetylation also reduces DNA-binding activity but does not affect interaction with PCNA or EP300.UniRule annotation1 Publication
Phosphorylation upon DNA damage induces relocalization to the nuclear plasma. Phosphorylation at Ser-187 by CDK2 occurs during late S-phase and results in dissociation from PCNA.UniRule annotation1 Publication
Methylation at Arg-192 by PRMT5 impedes Ser-187 phosphorylation and increases interaction with PCNA.UniRule annotation1 Publication

Keywords - PTMi

Acetylation, Methylation, Phosphoprotein

Proteomic databases

EPDiP39748.
PaxDbiP39748.
PeptideAtlasiP39748.
PRIDEiP39748.
TopDownProteomicsiP39748-1. [P39748-1]

PTM databases

iPTMnetiP39748.
PhosphoSitePlusiP39748.
SwissPalmiP39748.

Expressioni

Gene expression databases

BgeeiENSG00000168496.
CleanExiHS_FEN1.
ExpressionAtlasiP39748. baseline and differential.
GenevisibleiP39748. HS.

Organism-specific databases

HPAiCAB002262.
HPA006581.
HPA006748.

Interactioni

Subunit structurei

Three molecules of FEN1 bind to one PCNA trimer with each molecule binding to one PCNA monomer (PubMed:15616578). PCNA stimulates the nuclease activity without altering cleavage specificity (PubMed:15616578). The C-terminal domain binds EP300; can bind simultaneously to both PCNA and EP300 (PubMed:11430825). Interacts with PCNA; can bind simultaneously to both PCNA and EP300 (PubMed:9305916, PubMed:11430825). Interacts with DDX11; this interaction is direct and increases flap endonuclease activity of FEN1 (PubMed:18499658).UniRule annotation4 Publications

Binary interactionsi

WithEntry#Exp.IntActNotes
BLMP541324EBI-707816,EBI-621372
MUS81Q96NY95EBI-707816,EBI-2370806
PCNAP120046EBI-707816,EBI-358311
WRNQ141919EBI-707816,EBI-368417

Protein-protein interaction databases

BioGridi108528. 68 interactors.
DIPiDIP-24216N.
IntActiP39748. 28 interactors.
MINTiMINT-5004212.
STRINGi9606.ENSP00000305480.

Chemistry databases

BindingDBiP39748.

Structurei

Secondary structure

1380
Legend: HelixTurnBeta strandPDB Structure known for this area
Show more details
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Helixi6 – 13Combined sources8
Helixi15 – 17Combined sources3
Beta strandi18 – 22Combined sources5
Helixi23 – 26Combined sources4
Beta strandi30 – 34Combined sources5
Helixi35 – 45Combined sources11
Beta strandi47 – 52Combined sources6
Helixi62 – 75Combined sources14
Turni76 – 78Combined sources3
Beta strandi80 – 85Combined sources6
Helixi91 – 93Combined sources3
Helixi94 – 115Combined sources22
Helixi120 – 129Combined sources10
Helixi135 – 148Combined sources14
Beta strandi152 – 154Combined sources3
Helixi159 – 168Combined sources10
Beta strandi171 – 176Combined sources6
Helixi181 – 184Combined sources4
Beta strandi188 – 193Combined sources6
Beta strandi203 – 208Combined sources6
Helixi209 – 216Combined sources8
Helixi220 – 230Combined sources11
Beta strandi233 – 235Combined sources3
Helixi243 – 253Combined sources11
Helixi256 – 262Combined sources7
Turni265 – 267Combined sources3
Helixi276 – 284Combined sources9
Turni291 – 293Combined sources3
Helixi303 – 310Combined sources8
Turni311 – 314Combined sources4
Helixi318 – 335Combined sources18
Helixi340 – 342Combined sources3
Beta strandi344 – 351Combined sources8

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
1U7BX-ray1.88B331-350[»]
1UL1X-ray2.90X/Y/Z2-380[»]
3Q8KX-ray2.20A2-336[»]
3Q8LX-ray2.32A2-336[»]
3Q8MX-ray2.60A/B2-336[»]
3UVUX-ray2.38B352-370[»]
5E0VX-ray2.07C/D335-350[»]
5FV7X-ray2.84A/B1-336[»]
ProteinModelPortaliP39748.
SMRiP39748.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiP39748.

Family & Domainsi

Region

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Regioni1 – 104N-domainAdd BLAST104
Regioni122 – 253I-domainAdd BLAST132
Regioni336 – 344Interaction with PCNA1 Publication9

Sequence similaritiesi

Belongs to the XPG/RAD2 endonuclease family. FEN1 subfamily.UniRule annotation

Phylogenomic databases

eggNOGiKOG2519. Eukaryota.
COG0258. LUCA.
GeneTreeiENSGT00640000091478.
HOGENOMiHOG000193853.
HOVERGENiHBG000844.
InParanoidiP39748.
KOiK04799.
OMAiGSQDYDS.
OrthoDBiEOG091G0C0E.
PhylomeDBiP39748.
TreeFamiTF105701.

Family and domain databases

CDDicd09867. PIN_FEN1. 1 hit.
Gene3Di3.40.50.1010. 1 hit.
HAMAPiMF_00614. Fen. 1 hit.
InterProiIPR020045. 5-3_exonuclease_C.
IPR023426. Flap_endonuc.
IPR008918. HhH2.
IPR029060. PIN_domain-like.
IPR006086. XPG-I_dom.
IPR006084. XPG/Rad2.
IPR019974. XPG_CS.
IPR006085. XPG_DNA_repair_N.
[Graphical view]
PANTHERiPTHR11081. PTHR11081. 1 hit.
PfamiPF00867. XPG_I. 1 hit.
PF00752. XPG_N. 1 hit.
[Graphical view]
PRINTSiPR00853. XPGRADSUPER.
SMARTiSM00279. HhH2. 1 hit.
SM00484. XPGI. 1 hit.
SM00485. XPGN. 1 hit.
[Graphical view]
SUPFAMiSSF47807. SSF47807. 1 hit.
SSF88723. SSF88723. 1 hit.
PROSITEiPS00841. XPG_1. 1 hit.
PS00842. XPG_2. 1 hit.
[Graphical view]

Sequences (2)i

Sequence statusi: Complete.

This entry describes 2 isoformsi produced by alternative initiation. AlignAdd to basket

Isoform 1 (identifier: P39748-1) [UniParc]FASTAAdd to basket

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.

« Hide

        10         20         30         40         50
MGIQGLAKLI ADVAPSAIRE NDIKSYFGRK VAIDASMSIY QFLIAVRQGG
60 70 80 90 100
DVLQNEEGET TSHLMGMFYR TIRMMENGIK PVYVFDGKPP QLKSGELAKR
110 120 130 140 150
SERRAEAEKQ LQQAQAAGAE QEVEKFTKRL VKVTKQHNDE CKHLLSLMGI
160 170 180 190 200
PYLDAPSEAE ASCAALVKAG KVYAAATEDM DCLTFGSPVL MRHLTASEAK
210 220 230 240 250
KLPIQEFHLS RILQELGLNQ EQFVDLCILL GSDYCESIRG IGPKRAVDLI
260 270 280 290 300
QKHKSIEEIV RRLDPNKYPV PENWLHKEAH QLFLEPEVLD PESVELKWSE
310 320 330 340 350
PNEEELIKFM CGEKQFSEER IRSGVKRLSK SRQGSTQGRL DDFFKVTGSL
360 370 380
SSAKRKEPEP KGSTKKKAKT GAAGKFKRGK
Length:380
Mass (Da):42,593
Last modified:February 1, 1995 - v1
Checksum:i5154F2F6E57592C5
GO
Isoform FENMIT (identifier: P39748-2) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     1-64: Missing.

Note: No nuclease activity. Binds preferentially to RNA flap structures and R-loops.
Show »
Length:316
Mass (Da):35,673
Checksum:i7D5CA94548F0ED99
GO

Alternative sequence

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Alternative sequenceiVSP_0475201 – 64Missing in isoform FENMIT. CuratedAdd BLAST64

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
X76771 mRNA. Translation: CAA54166.1.
L37374 mRNA. Translation: AAA91331.1.
AF523117 Genomic DNA. Translation: AAM74238.1.
AC004770 Genomic DNA. Translation: AAC23394.1.
BC000323 mRNA. Translation: AAH00323.1.
CCDSiCCDS8010.1. [P39748-1]
PIRiA56531.
RefSeqiNP_004102.1. NM_004111.5. [P39748-1]
UniGeneiHs.409065.

Genome annotation databases

EnsembliENST00000305885; ENSP00000305480; ENSG00000168496. [P39748-1]
GeneIDi2237.
KEGGihsa:2237.

Keywords - Coding sequence diversityi

Alternative initiation

Cross-referencesi

Web resourcesi

NIEHS-SNPs
Atlas of Genetics and Cytogenetics in Oncology and Haematology

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
X76771 mRNA. Translation: CAA54166.1.
L37374 mRNA. Translation: AAA91331.1.
AF523117 Genomic DNA. Translation: AAM74238.1.
AC004770 Genomic DNA. Translation: AAC23394.1.
BC000323 mRNA. Translation: AAH00323.1.
CCDSiCCDS8010.1. [P39748-1]
PIRiA56531.
RefSeqiNP_004102.1. NM_004111.5. [P39748-1]
UniGeneiHs.409065.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
1U7BX-ray1.88B331-350[»]
1UL1X-ray2.90X/Y/Z2-380[»]
3Q8KX-ray2.20A2-336[»]
3Q8LX-ray2.32A2-336[»]
3Q8MX-ray2.60A/B2-336[»]
3UVUX-ray2.38B352-370[»]
5E0VX-ray2.07C/D335-350[»]
5FV7X-ray2.84A/B1-336[»]
ProteinModelPortaliP39748.
SMRiP39748.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi108528. 68 interactors.
DIPiDIP-24216N.
IntActiP39748. 28 interactors.
MINTiMINT-5004212.
STRINGi9606.ENSP00000305480.

Chemistry databases

BindingDBiP39748.
ChEMBLiCHEMBL5027.

PTM databases

iPTMnetiP39748.
PhosphoSitePlusiP39748.
SwissPalmiP39748.

Polymorphism and mutation databases

BioMutaiFEN1.
DMDMi729475.

Proteomic databases

EPDiP39748.
PaxDbiP39748.
PeptideAtlasiP39748.
PRIDEiP39748.
TopDownProteomicsiP39748-1. [P39748-1]

Protocols and materials databases

DNASUi2237.
Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000305885; ENSP00000305480; ENSG00000168496. [P39748-1]
GeneIDi2237.
KEGGihsa:2237.

Organism-specific databases

CTDi2237.
DisGeNETi2237.
GeneCardsiFEN1.
HGNCiHGNC:3650. FEN1.
HPAiCAB002262.
HPA006581.
HPA006748.
MIMi600393. gene.
neXtProtiNX_P39748.
OpenTargetsiENSG00000168496.
PharmGKBiPA28090.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiKOG2519. Eukaryota.
COG0258. LUCA.
GeneTreeiENSGT00640000091478.
HOGENOMiHOG000193853.
HOVERGENiHBG000844.
InParanoidiP39748.
KOiK04799.
OMAiGSQDYDS.
OrthoDBiEOG091G0C0E.
PhylomeDBiP39748.
TreeFamiTF105701.

Enzyme and pathway databases

BioCyciZFISH:HS09774-MONOMER.
ReactomeiR-HSA-110362. POLB-Dependent Long Patch Base Excision Repair.
R-HSA-162594. Early Phase of HIV Life Cycle.
R-HSA-174437. Removal of the Flap Intermediate from the C-strand.
R-HSA-5651801. PCNA-Dependent Long Patch Base Excision Repair.
R-HSA-5685939. HDR through MMEJ (alt-NHEJ).
R-HSA-69166. Removal of the Flap Intermediate.
SignaLinkiP39748.
SIGNORiP39748.

Miscellaneous databases

ChiTaRSiFEN1. human.
EvolutionaryTraceiP39748.
GeneWikiiFlap_structure-specific_endonuclease_1.
GenomeRNAii2237.
PROiP39748.
SOURCEiSearch...

Gene expression databases

BgeeiENSG00000168496.
CleanExiHS_FEN1.
ExpressionAtlasiP39748. baseline and differential.
GenevisibleiP39748. HS.

Family and domain databases

CDDicd09867. PIN_FEN1. 1 hit.
Gene3Di3.40.50.1010. 1 hit.
HAMAPiMF_00614. Fen. 1 hit.
InterProiIPR020045. 5-3_exonuclease_C.
IPR023426. Flap_endonuc.
IPR008918. HhH2.
IPR029060. PIN_domain-like.
IPR006086. XPG-I_dom.
IPR006084. XPG/Rad2.
IPR019974. XPG_CS.
IPR006085. XPG_DNA_repair_N.
[Graphical view]
PANTHERiPTHR11081. PTHR11081. 1 hit.
PfamiPF00867. XPG_I. 1 hit.
PF00752. XPG_N. 1 hit.
[Graphical view]
PRINTSiPR00853. XPGRADSUPER.
SMARTiSM00279. HhH2. 1 hit.
SM00484. XPGI. 1 hit.
SM00485. XPGN. 1 hit.
[Graphical view]
SUPFAMiSSF47807. SSF47807. 1 hit.
SSF88723. SSF88723. 1 hit.
PROSITEiPS00841. XPG_1. 1 hit.
PS00842. XPG_2. 1 hit.
[Graphical view]
ProtoNetiSearch...

Entry informationi

Entry nameiFEN1_HUMAN
AccessioniPrimary (citable) accession number: P39748
Entry historyi
Integrated into UniProtKB/Swiss-Prot: February 1, 1995
Last sequence update: February 1, 1995
Last modified: November 30, 2016
This is version 171 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 chromosome 11
    Human chromosome 11: entries, gene names and cross-references to MIM
  2. MIM cross-references
    Online Mendelian Inheritance in Man (MIM) cross-references in UniProtKB/Swiss-Prot
  3. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  4. 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.