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Protein

O-phosphoseryl-tRNA(Sec) selenium transferase

Gene

SEPSECS

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

Functioni

Converts O-phosphoseryl-tRNA(Sec) to selenocysteinyl-tRNA(Sec) required for selenoprotein biosynthesis.1 Publication

Catalytic activityi

O-phospho-L-seryl-tRNA(Sec) + selenophosphate + H2O = L-selenocysteinyl-tRNA(Sec) + 2 phosphate.1 Publication

Cofactori

pyridoxal 5'-phosphate2 Publications

Pathwayi: selenocysteinyl-tRNA(Sec) biosynthesis

This protein is involved in step 2 of the subpathway that synthesizes selenocysteinyl-tRNA(Sec) from L-seryl-tRNA(Sec) (archaeal/eukaryal route).1 Publication
Proteins known to be involved in the 2 steps of the subpathway in this organism are:
  1. L-seryl-tRNA(Sec) kinase (PSTK)
  2. O-phosphoseryl-tRNA(Sec) selenium transferase, O-phosphoseryl-tRNA(Sec) selenium transferase (SEPSECS), O-phosphoseryl-tRNA(Sec) selenium transferase (SEPSECS)
This subpathway is part of the pathway selenocysteinyl-tRNA(Sec) biosynthesis, which is itself part of Aminoacyl-tRNA biosynthesis.
View all proteins of this organism that are known to be involved in the subpathway that synthesizes selenocysteinyl-tRNA(Sec) from L-seryl-tRNA(Sec) (archaeal/eukaryal route), the pathway selenocysteinyl-tRNA(Sec) biosynthesis and in Aminoacyl-tRNA biosynthesis.

Sites

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sitei74May act as a substrate filter by repelling compounds with a negatively charged alpha-carboxylateBy similarity1
Binding sitei75Pyridoxal phosphate1 Publication1
Binding sitei97Substrate1 Publication1
Binding sitei98Substrate1 Publication1
Binding sitei105Substrate1 Publication1
Binding sitei271tRNA variable arm1 Publication1
Binding sitei313Substrate1 Publication1
Binding sitei398tRNA discriminator base1 Publication1
Binding sitei463tRNA acceptor arm1 Publication1

GO - Molecular functioni

GO - Biological processi

Complete GO annotation...

Keywords - Molecular functioni

Transferase

Keywords - Biological processi

Protein biosynthesis

Keywords - Ligandi

Pyridoxal phosphate, RNA-binding, Selenium, tRNA-binding

Enzyme and pathway databases

BioCyciZFISH:HS03243-MONOMER.
BRENDAi2.9.1.2. 2681.
ReactomeiR-HSA-2408557. Selenocysteine synthesis.
UniPathwayiUPA00906; UER00898.

Names & Taxonomyi

Protein namesi
Recommended name:
O-phosphoseryl-tRNA(Sec) selenium transferase (EC:2.9.1.21 Publication)
Alternative name(s):
Liver-pancreas antigen
Short name:
LP
SLA-p35
SLA/LP autoantigen
Selenocysteine synthase
Short name:
Sec synthase
Selenocysteinyl-tRNA(Sec) synthase
Sep-tRNA:Sec-tRNA synthase
Short name:
SepSecS
Soluble liver antigen
Short name:
SLA
UGA suppressor tRNA-associated protein
tRNA(Ser/Sec)-associated antigenic protein
Gene namesi
Name:SEPSECS
Synonyms:TRNP48
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
Proteomesi
  • UP000005640 Componenti: Chromosome 4

Organism-specific databases

HGNCiHGNC:30605. SEPSECS.

Subcellular locationi

GO - Cellular componenti

Complete GO annotation...

Keywords - Cellular componenti

Cytoplasm

Pathology & Biotechi

Involvement in diseasei

Pontocerebellar hypoplasia 2D (PCH2D)2 Publications
The disease is caused by mutations affecting the gene represented in this entry.
Disease descriptionA disorder characterized by postnatal onset of progressive atrophy of the cerebrum and cerebellum, microcephaly, profound mental retardation, spasticity, and variable seizures.
See also OMIM:613811
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Natural variantiVAR_065585239A → T in PCH2D; abrogates enzyme activity. 1 PublicationCorresponds to variant rs267607035dbSNPEnsembl.1
Natural variantiVAR_074163325T → S in PCH2D. 1 Publication1
Natural variantiVAR_065586334Y → C in PCH2D; abrogates enzyme activity. 1 PublicationCorresponds to variant rs267607036dbSNPEnsembl.1

Mutagenesis

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Mutagenesisi75R → A: Inactive in vivo. 1 Publication1
Mutagenesisi97R → A: Indistinguishable from wild-type. 1 Publication1
Mutagenesisi97R → Q: Indistinguishable from wild-type. 1 Publication1
Mutagenesisi105Q → A: Inactive in vivo. 1 Publication1
Mutagenesisi173K → A: Indistinguishable from wild-type. 1 Publication1
Mutagenesisi173K → M: Indistinguishable from wild-type. 1 Publication1
Mutagenesisi284K → A: Loss of activity. 1 Publication1
Mutagenesisi313R → A: Inactive in vivo. 1 Publication1

Keywords - Diseasei

Disease mutation, Epilepsy, Mental retardation, Neurodegeneration

Organism-specific databases

DisGeNETi51091.
MalaCardsiSEPSECS.
MIMi613811. phenotype.
OpenTargetsiENSG00000109618.
Orphaneti2524. Pontocerebellar hypoplasia type 2.
247198. Progressive cerebello-cerebral atrophy.
PharmGKBiPA162402915.

Polymorphism and mutation databases

BioMutaiSEPSECS.
DMDMi62287911.

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
ChainiPRO_00002198751 – 501O-phosphoseryl-tRNA(Sec) selenium transferaseAdd BLAST501

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Modified residuei14PhosphoserineCombined sources1
Modified residuei284N6-(pyridoxal phosphate)lysine1 Publication1

Keywords - PTMi

Phosphoprotein

Proteomic databases

EPDiQ9HD40.
MaxQBiQ9HD40.
PaxDbiQ9HD40.
PeptideAtlasiQ9HD40.
PRIDEiQ9HD40.

PTM databases

iPTMnetiQ9HD40.
PhosphoSitePlusiQ9HD40.

Expressioni

Tissue specificityi

Primarily expressed in liver, pancreas, kidney and lung. Overexpressed in PHA-stimulated T-cells.

Gene expression databases

BgeeiENSG00000109618.
CleanExiHS_SEPSECS.
ExpressionAtlasiQ9HD40. baseline and differential.
GenevisibleiQ9HD40. HS.

Organism-specific databases

HPAiCAB002500.
CAB010893.

Interactioni

Subunit structurei

Homotetramer formed by a catalytic dimer and a non-catalytic dimer serving as a binding platform that orients tRNASec for catalysis. Each tetramer binds the CCA ends of two tRNAs which point to the active sites of the catalytic dimer.1 Publication

Binary interactionsi

WithEntry#Exp.IntActNotes
gagP045913EBI-6163446,EBI-6163428From a different organism.

Protein-protein interaction databases

BioGridi119280. 7 interactors.
IntActiQ9HD40. 6 interactors.
STRINGi9606.ENSP00000371535.

Structurei

Secondary structure

1501
Legend: HelixTurnBeta strandPDB Structure known for this area
Show more details
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Helixi3 – 10Combined sources8
Helixi22 – 38Combined sources17
Helixi48 – 59Combined sources12
Helixi63 – 65Combined sources3
Helixi82 – 87Combined sources6
Turni88 – 90Combined sources3
Beta strandi95 – 97Combined sources3
Beta strandi100 – 103Combined sources4
Helixi109 – 128Combined sources20
Beta strandi136 – 142Combined sources7
Helixi144 – 158Combined sources15
Beta strandi164 – 168Combined sources5
Helixi173 – 181Combined sources9
Beta strandi185 – 189Combined sources5
Beta strandi191 – 194Combined sources4
Beta strandi197 – 200Combined sources4
Helixi202 – 212Combined sources11
Helixi214 – 216Combined sources3
Beta strandi217 – 225Combined sources9
Helixi235 – 244Combined sources10
Beta strandi249 – 252Combined sources4
Helixi260 – 272Combined sources13
Beta strandi277 – 281Combined sources5
Helixi282 – 286Combined sources5
Beta strandi293 – 298Combined sources6
Helixi300 – 308Combined sources9
Helixi317 – 357Combined sources41
Turni358 – 360Combined sources3
Beta strandi370 – 376Combined sources7
Turni382 – 384Combined sources3
Helixi388 – 397Combined sources10
Beta strandi404 – 406Combined sources3
Beta strandi411 – 414Combined sources4
Beta strandi417 – 420Combined sources4
Turni421 – 425Combined sources5
Beta strandi426 – 428Combined sources3
Beta strandi433 – 437Combined sources5
Helixi444 – 461Combined sources18

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
3HL2X-ray2.81A/B/C/D1-501[»]
4ZDLX-ray2.26A/B1-501[»]
4ZDOX-ray2.65A/B/C/D1-501[»]
4ZDPX-ray2.70A/B/C/D1-501[»]
ProteinModelPortaliQ9HD40.
SMRiQ9HD40.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiQ9HD40.

Family & Domainsi

Region

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Regioni1 – 44Tetramerization1 PublicationAdd BLAST44
Regioni96 – 106Phosphate loop (P-loop)1 PublicationAdd BLAST11
Regioni474 – 493SLA/LP epitope1 PublicationAdd BLAST20

Sequence similaritiesi

Belongs to the SepSecS family.Curated

Phylogenomic databases

eggNOGiKOG3843. Eukaryota.
COG0076. LUCA.
GeneTreeiENSGT00390000007332.
HOGENOMiHOG000254245.
HOVERGENiHBG061363.
InParanoidiQ9HD40.
KOiK03341.
OMAiPCPYLNA.
OrthoDBiEOG091G071Q.
PhylomeDBiQ9HD40.
TreeFamiTF314381.

Family and domain databases

Gene3Di3.40.640.10. 1 hit.
InterProiIPR019793. Peroxidases_heam-ligand_BS.
IPR015424. PyrdxlP-dep_Trfase.
IPR015421. PyrdxlP-dep_Trfase_major_sub1.
IPR019872. Sec-tRNA_Se_transferase.
IPR008829. SepSecS/SepCysS.
[Graphical view]
PANTHERiPTHR12944. PTHR12944. 1 hit.
PfamiPF05889. SepSecS. 1 hit.
[Graphical view]
PIRSFiPIRSF017689. SepSecS. 1 hit.
SUPFAMiSSF53383. SSF53383. 1 hit.
TIGRFAMsiTIGR03531. selenium_SpcS. 1 hit.

Sequences (3)i

Sequence statusi: Complete.

This entry describes 3 isoformsi produced by alternative splicing. AlignAdd to basket

Isoform 1 (identifier: Q9HD40-1) [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
MNRESFAAGE RLVSPAYVRQ GCEARRSHEH LIRLLLEKGK CPENGWDEST
60 70 80 90 100
LELFLHELAI MDSNNFLGNC GVGEREGRVA SALVARRHYR FIHGIGRSGD
110 120 130 140 150
ISAVQPKAAG SSLLNKITNS LVLDIIKLAG VHTVANCFVV PMATGMSLTL
160 170 180 190 200
CFLTLRHKRP KAKYIIWPRI DQKSCFKSMI TAGFEPVVIE NVLEGDELRT
210 220 230 240 250
DLKAVEAKVQ ELGPDCILCI HSTTSCFAPR VPDRLEELAV ICANYDIPHI
260 270 280 290 300
VNNAYGVQSS KCMHLIQQGA RVGRIDAFVQ SLDKNFMVPV GGAIIAGFND
310 320 330 340 350
SFIQEISKMY PGRASASPSL DVLITLLSLG SNGYKKLLKE RKEMFSYLSN
360 370 380 390 400
QIKKLSEAYN ERLLHTPHNP ISLAMTLKTL DEHRDKAVTQ LGSMLFTRQV
410 420 430 440 450
SGARVVPLGS MQTVSGYTFR GFMSHTNNYP CAYLNAASAI GMKMQDVDLF
460 470 480 490 500
IKRLDRCLKA VRKERSKESD DNYDKTEDVD IEEMALKLDN VLLDTYQDAS

S
Length:501
Mass (Da):55,726
Last modified:March 29, 2005 - v2
Checksum:i7136FB390B18760B
GO
Isoform 2 (identifier: Q9HD40-2) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     39-47: GKCPENGWD → VHSWHWTIR
     48-501: Missing.

Note: May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. No experimental confirmation available.
Show »
Length:47
Mass (Da):5,627
Checksum:i958F3F91D272149B
GO
Isoform 3 (identifier: Q9HD40-3) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     1-38: MNRESFAAGERLVSPAYVRQGCEARRSHEHLIRLLLEK → MQCDDLGSLQPPPPGFTPFACLSLPSSWDYRRPPPHP

Show »
Length:500
Mass (Da):55,411
Checksum:i82AE23050D9C2011
GO

Sequence cautioni

The sequence AAD33963 differs from that shown. Reason: Erroneous translation. Wrong choice of CDS.Curated
The sequence AAH23539 differs from that shown. Reason: Erroneous translation. Wrong choice of CDS.Curated
The sequence CAB62209 differs from that shown. Reason: Erroneous initiation. Translation N-terminally shortened.Curated
The sequence CAB89517 differs from that shown. Reason: Frameshift at position 39.Curated

Experimental Info

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sequence conflicti98S → P in AAG00491 (Ref. 8) Curated1
Sequence conflicti264H → R in BAF85165 (PubMed:14702039).Curated1
Sequence conflicti398R → K in AAD33963 (PubMed:10801173).Curated1
Sequence conflicti398R → K in CAB89517 (PubMed:10801173).Curated1
Sequence conflicti452K → N in AAD33963 (PubMed:10801173).Curated1
Sequence conflicti452K → N in CAB89517 (PubMed:10801173).Curated1
Sequence conflicti467K → R in AAG00491 (Ref. 8) Curated1

Natural variant

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Natural variantiVAR_065585239A → T in PCH2D; abrogates enzyme activity. 1 PublicationCorresponds to variant rs267607035dbSNPEnsembl.1
Natural variantiVAR_074163325T → S in PCH2D. 1 Publication1
Natural variantiVAR_065586334Y → C in PCH2D; abrogates enzyme activity. 1 PublicationCorresponds to variant rs267607036dbSNPEnsembl.1

Alternative sequence

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Alternative sequenceiVSP_0380801 – 38MNRES…LLLEK → MQCDDLGSLQPPPPGFTPFA CLSLPSSWDYRRPPPHP in isoform 3. 1 PublicationAdd BLAST38
Alternative sequenceiVSP_03807839 – 47GKCPENGWD → VHSWHWTIR in isoform 2. 2 Publications9
Alternative sequenceiVSP_03807948 – 501Missing in isoform 2. 2 PublicationsAdd BLAST454

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AK292476 mRNA. Translation: BAF85165.1.
BX648976 mRNA. No translation available.
AC007073 Genomic DNA. No translation available.
AC104662 Genomic DNA. No translation available.
CH471069 Genomic DNA. Translation: EAW92832.1.
BC023539 mRNA. Translation: AAH23539.1. Sequence problems.
BC117202 mRNA. Translation: AAI17203.1.
AF146396 mRNA. Translation: AAD33963.2. Sequence problems.
AJ277541 mRNA. Translation: CAB89517.1. Frameshift.
AJ238617 mRNA. Translation: CAB62209.1. Different initiation.
AF282065 mRNA. Translation: AAG00491.1.
CCDSiCCDS3432.2. [Q9HD40-1]
RefSeqiNP_058651.3. NM_016955.3. [Q9HD40-1]
XP_011512148.1. XM_011513846.2. [Q9HD40-3]
XP_011512150.1. XM_011513848.1.
UniGeneiHs.253305.

Genome annotation databases

EnsembliENST00000382103; ENSP00000371535; ENSG00000109618. [Q9HD40-1]
ENST00000514585; ENSP00000421880; ENSG00000109618. [Q9HD40-2]
GeneIDi51091.
KEGGihsa:51091.
UCSCiuc003grg.4. human. [Q9HD40-1]

Keywords - Coding sequence diversityi

Alternative splicing

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AK292476 mRNA. Translation: BAF85165.1.
BX648976 mRNA. No translation available.
AC007073 Genomic DNA. No translation available.
AC104662 Genomic DNA. No translation available.
CH471069 Genomic DNA. Translation: EAW92832.1.
BC023539 mRNA. Translation: AAH23539.1. Sequence problems.
BC117202 mRNA. Translation: AAI17203.1.
AF146396 mRNA. Translation: AAD33963.2. Sequence problems.
AJ277541 mRNA. Translation: CAB89517.1. Frameshift.
AJ238617 mRNA. Translation: CAB62209.1. Different initiation.
AF282065 mRNA. Translation: AAG00491.1.
CCDSiCCDS3432.2. [Q9HD40-1]
RefSeqiNP_058651.3. NM_016955.3. [Q9HD40-1]
XP_011512148.1. XM_011513846.2. [Q9HD40-3]
XP_011512150.1. XM_011513848.1.
UniGeneiHs.253305.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
3HL2X-ray2.81A/B/C/D1-501[»]
4ZDLX-ray2.26A/B1-501[»]
4ZDOX-ray2.65A/B/C/D1-501[»]
4ZDPX-ray2.70A/B/C/D1-501[»]
ProteinModelPortaliQ9HD40.
SMRiQ9HD40.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi119280. 7 interactors.
IntActiQ9HD40. 6 interactors.
STRINGi9606.ENSP00000371535.

PTM databases

iPTMnetiQ9HD40.
PhosphoSitePlusiQ9HD40.

Polymorphism and mutation databases

BioMutaiSEPSECS.
DMDMi62287911.

Proteomic databases

EPDiQ9HD40.
MaxQBiQ9HD40.
PaxDbiQ9HD40.
PeptideAtlasiQ9HD40.
PRIDEiQ9HD40.

Protocols and materials databases

DNASUi51091.
Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000382103; ENSP00000371535; ENSG00000109618. [Q9HD40-1]
ENST00000514585; ENSP00000421880; ENSG00000109618. [Q9HD40-2]
GeneIDi51091.
KEGGihsa:51091.
UCSCiuc003grg.4. human. [Q9HD40-1]

Organism-specific databases

CTDi51091.
DisGeNETi51091.
GeneCardsiSEPSECS.
HGNCiHGNC:30605. SEPSECS.
HPAiCAB002500.
CAB010893.
MalaCardsiSEPSECS.
MIMi613009. gene.
613811. phenotype.
neXtProtiNX_Q9HD40.
OpenTargetsiENSG00000109618.
Orphaneti2524. Pontocerebellar hypoplasia type 2.
247198. Progressive cerebello-cerebral atrophy.
PharmGKBiPA162402915.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiKOG3843. Eukaryota.
COG0076. LUCA.
GeneTreeiENSGT00390000007332.
HOGENOMiHOG000254245.
HOVERGENiHBG061363.
InParanoidiQ9HD40.
KOiK03341.
OMAiPCPYLNA.
OrthoDBiEOG091G071Q.
PhylomeDBiQ9HD40.
TreeFamiTF314381.

Enzyme and pathway databases

UniPathwayiUPA00906; UER00898.
BioCyciZFISH:HS03243-MONOMER.
BRENDAi2.9.1.2. 2681.
ReactomeiR-HSA-2408557. Selenocysteine synthesis.

Miscellaneous databases

EvolutionaryTraceiQ9HD40.
GeneWikiiSEPSECS.
GenomeRNAii51091.
PROiQ9HD40.
SOURCEiSearch...

Gene expression databases

BgeeiENSG00000109618.
CleanExiHS_SEPSECS.
ExpressionAtlasiQ9HD40. baseline and differential.
GenevisibleiQ9HD40. HS.

Family and domain databases

Gene3Di3.40.640.10. 1 hit.
InterProiIPR019793. Peroxidases_heam-ligand_BS.
IPR015424. PyrdxlP-dep_Trfase.
IPR015421. PyrdxlP-dep_Trfase_major_sub1.
IPR019872. Sec-tRNA_Se_transferase.
IPR008829. SepSecS/SepCysS.
[Graphical view]
PANTHERiPTHR12944. PTHR12944. 1 hit.
PfamiPF05889. SepSecS. 1 hit.
[Graphical view]
PIRSFiPIRSF017689. SepSecS. 1 hit.
SUPFAMiSSF53383. SSF53383. 1 hit.
TIGRFAMsiTIGR03531. selenium_SpcS. 1 hit.
ProtoNetiSearch...

Entry informationi

Entry nameiSPCS_HUMAN
AccessioniPrimary (citable) accession number: Q9HD40
Secondary accession number(s): A8K8W1
, Q0D2P3, Q17RT1, Q9NXZ5, Q9UGM9, Q9Y353
Entry historyi
Integrated into UniProtKB/Swiss-Prot: March 29, 2005
Last sequence update: March 29, 2005
Last modified: November 30, 2016
This is version 134 of the entry and version 2 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

Miscellaneous

Possible diagnostic marker for autoimmune hepatitis (AIH).

Keywords - Technical termi

3D-structure, Complete proteome, Reference proteome

Documents

  1. Human chromosome 4
    Human chromosome 4: entries, gene names and cross-references to MIM
  2. Human entries with polymorphisms or disease mutations
    List of human entries with polymorphisms or disease mutations
  3. Human polymorphisms and disease mutations
    Index of human polymorphisms and disease mutations
  4. MIM cross-references
    Online Mendelian Inheritance in Man (MIM) cross-references in UniProtKB/Swiss-Prot
  5. PATHWAY comments
    Index of metabolic and biosynthesis pathways
  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.