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Protein

Presenilin homolog

Gene

Psn

Organism
Drosophila melanogaster (Fruit fly)
Status
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli

Functioni

Probable catalytic subunit of the gamma-secretase complex, an endoprotease complex that catalyzes the intramembrane cleavage of integral membrane proteins such as Notch receptor. Required for S3 cleavage of Notch, which releases activated Notch protein from the cell membrane. Involved in the patterning of the optic lobes.3 Publications

Sites

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Active sitei279 – 2791By similarity
Active sitei461 – 4611By similarity

GO - Molecular functioni

  • aspartic-type endopeptidase activity Source: InterPro
  • protein homodimerization activity Source: FlyBase

GO - Biological processi

  • apoptotic process Source: CACAO
  • copper ion import Source: FlyBase
  • cytoskeleton organization Source: FlyBase
  • lateral inhibition Source: FlyBase
  • membrane protein ectodomain proteolysis Source: FlyBase
  • neuron projection morphogenesis Source: FlyBase
  • Notch receptor processing Source: FlyBase
  • Notch signaling pathway Source: FlyBase
  • protein processing Source: InterPro
  • regulation of heart rate Source: FlyBase
  • regulation of Notch signaling pathway Source: FlyBase
  • single organismal cell-cell adhesion Source: FlyBase
  • wing disc dorsal/ventral pattern formation Source: FlyBase
Complete GO annotation...

Keywords - Molecular functioni

Hydrolase, Protease

Keywords - Biological processi

Notch signaling pathway

Enzyme and pathway databases

ReactomeiR-DME-1980148. Signaling by NOTCH3.
R-DME-1980150. Signaling by NOTCH4.
R-DME-3928665. EPH-ephrin mediated repulsion of cells.
SignaLinkiO02194.

Protein family/group databases

MEROPSiA22.014.

Names & Taxonomyi

Protein namesi
Recommended name:
Presenilin homolog (EC:3.4.23.-)
Short name:
DmPS
Alternative name(s):
dPS
Gene namesi
Name:Psn
Synonyms:PS
ORF Names:CG18803
OrganismiDrosophila melanogaster (Fruit fly)
Taxonomic identifieri7227 [NCBI]
Taxonomic lineageiEukaryotaMetazoaEcdysozoaArthropodaHexapodaInsectaPterygotaNeopteraEndopterygotaDipteraBrachyceraMuscomorphaEphydroideaDrosophilidaeDrosophilaSophophora
Proteomesi
  • UP000000803 Componenti: Chromosome 3L

Organism-specific databases

FlyBaseiFBgn0019947. Psn.

Subcellular locationi

Topology

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Topological domaini1 – 106106CytoplasmicSequence analysisAdd
BLAST
Transmembranei107 – 12721Helical; Name=1Sequence analysisAdd
BLAST
Topological domaini128 – 15427LumenalSequence analysisAdd
BLAST
Transmembranei155 – 17521Helical; Name=2Sequence analysisAdd
BLAST
Topological domaini176 – 1827CytoplasmicSequence analysis
Transmembranei183 – 20321Helical; Name=3Sequence analysisAdd
BLAST
Topological domaini204 – 21613LumenalSequence analysisAdd
BLAST
Transmembranei217 – 23721Helical; Name=4Sequence analysisAdd
BLAST
Topological domaini238 – 2425CytoplasmicSequence analysis
Transmembranei243 – 26321Helical; Name=5Sequence analysisAdd
BLAST
Topological domaini264 – 2652LumenalSequence analysis
Transmembranei266 – 28621Helical; Name=6Sequence analysisAdd
BLAST
Topological domaini287 – 453167CytoplasmicSequence analysisAdd
BLAST
Transmembranei454 – 47421Helical; Name=7Sequence analysisAdd
BLAST
Topological domaini475 – 4817LumenalSequence analysis
Transmembranei482 – 50221Helical; Name=8Sequence analysisAdd
BLAST
Topological domaini503 – 5064CytoplasmicSequence analysis
Intramembranei507 – 52721Helical; Name=9Sequence analysisAdd
BLAST
Topological domaini528 – 54114CytoplasmicSequence analysisAdd
BLAST

GO - Cellular componenti

  • apical plasma membrane Source: FlyBase
  • cell cortex Source: FlyBase
  • cytoplasm Source: FlyBase
  • endoplasmic reticulum membrane Source: UniProtKB-SubCell
  • gamma-secretase complex Source: FlyBase
  • Golgi membrane Source: UniProtKB-SubCell
  • integral component of plasma membrane Source: FlyBase
  • late endosome Source: FlyBase
  • recycling endosome Source: FlyBase
Complete GO annotation...

Keywords - Cellular componenti

Endoplasmic reticulum, Golgi apparatus, Membrane

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Chaini1 – 541541Presenilin homologPRO_0000073901Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Glycosylationi129 – 1291N-linked (GlcNAc...)Sequence analysis

Post-translational modificationi

Cleaved. The cleavage, which probably takes place between the 6th and the 7th transmembrane regions, may be required for activation of the gamma-secretase activity.1 Publication

Keywords - PTMi

Glycoprotein

Proteomic databases

PaxDbiO02194.
PRIDEiO02194.

Expressioni

Tissue specificityi

Maternally expressed in nurse and follicle cells. In early embryos, expressed in all or most cells and later increases in CNS and epidermal tissues. In larvae, expression is seen in all imaginal disks, brain and optic lobes. In pupae, expression is seen in eye disk and brain.1 Publication

Developmental stagei

Expressed both maternally and zygotically throughout development.4 Publications

Gene expression databases

BgeeiO02194.
ExpressionAtlasiO02194. differential.
GenevisibleiO02194. DM.

Interactioni

Subunit structurei

Homodimer (By similarity). Component of the gamma-secretase complex, a complex composed of a presenilin (Psn) homodimer, nicastrin (Nct), Aph-1 and Pen-2. Interacts with Metl. Isoform 2 shows a better interaction with Metl than isoform 1.By similarity2 Publications

GO - Molecular functioni

  • protein homodimerization activity Source: FlyBase

Protein-protein interaction databases

BioGridi65518. 11 interactions.
DIPiDIP-1139N.
STRINGi7227.FBpp0077850.

Structurei

3D structure databases

ProteinModelPortaliO02194.
SMRiO02194. Positions 401-541.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Region

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Regioni320 – 481162Interaction with metlAdd
BLAST

Motif

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Motifi507 – 5093PAL

Domaini

The PAL motif is required for normal active site conformation.By similarity

Sequence similaritiesi

Belongs to the peptidase A22A family.Curated

Keywords - Domaini

Transmembrane, Transmembrane helix

Phylogenomic databases

eggNOGiKOG2736. Eukaryota.
ENOG410XPZD. LUCA.
GeneTreeiENSGT00390000016593.
InParanoidiO02194.
KOiK04505.
OMAiIEQHEEG.
OrthoDBiEOG7NGQBG.
PhylomeDBiO02194.

Family and domain databases

InterProiIPR001108. Peptidase_A22A.
IPR006639. Preselin/SPP.
[Graphical view]
PANTHERiPTHR10202. PTHR10202. 1 hit.
PfamiPF01080. Presenilin. 1 hit.
[Graphical view]
PRINTSiPR01072. PRESENILIN.
SMARTiSM00730. PSN. 1 hit.
[Graphical view]

Sequences (3)i

Sequence statusi: Complete.

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

Isoform 1 (identifier: O02194-1) [UniParc]FASTAAdd to basket

Also known as: A2, A, DLA-b

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
MAAVNLQASC SSGLASEDDA NVGSQIGAAE RLERPPRRQQ QRNNYGSSNQ
60 70 80 90 100
DQPDAAILAV PNVVMREPCG SRPSRLTGGG GGSGGPPTNE MEEEQGLKYG
110 120 130 140 150
AQHVIKLFVP VSLCMLVVVA TINSISFYNS TDVYLLYTPF HEQSPEPSVK
160 170 180 190 200
FWSALANSLI LMSVVVVMTF LLIVLYKKRC YRIIHGWLIL SSFMLLFIFT
210 220 230 240 250
YLYLEELLRA YNIPMDYPTA LLIMWNFGVV GMMSIHWQGP LRLQQGYLIF
260 270 280 290 300
VAALMALVFI KYLPEWTAWA VLAAISIWDL IAVLSPRGPL RILVETAQER
310 320 330 340 350
NEQIFPALIY SSTVVYALVN TVTPQQSQAT ASSSPSSSNS TTTTRATQNS
360 370 380 390 400
LASPEAAAAS GQRTGNSHPR QNQRDDGSVL ATEGMPLVTF KSNLRGNAEA
410 420 430 440 450
AGFTQEWSAN LSERVARRQI EVQSTQSGNA QRSNEYRTVT APDQNHPDGQ
460 470 480 490 500
EERGIKLGLG DFIFYSVLVG KASSYGDWTT TIACFVAILI GLCLTLLLLA
510 520 530 540
IWRKALPALP ISITFGLIFC FATSAVVKPF MEDLSAKQVF I
Length:541
Mass (Da):59,304
Last modified:July 15, 1999 - v2
Checksum:iA3B3D54348A2C03F
GO
Isoform 2 (identifier: O02194-2) [UniParc]FASTAAdd to basket

Also known as: A1, B, PS-d, DLA-a

The sequence of this isoform differs from the canonical sequence as follows:
     384-397: Missing.

Show »
Length:527
Mass (Da):57,788
Checksum:i7C74C25FA9730462
GO
Isoform 3 (identifier: O02194-3) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     365-397: Missing.

Show »
Length:508
Mass (Da):55,725
Checksum:iA82F7261B9CABF39
GO

Experimental Info

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sequence conflicti80 – 812GG → RS in AAB53369 (PubMed:9106743).Curated

Alternative sequence

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Alternative sequencei365 – 39733Missing in isoform 3. CuratedVSP_007988Add
BLAST
Alternative sequencei384 – 39714Missing in isoform 2. 1 PublicationVSP_005195Add
BLAST

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
U77934 mRNA. Translation: AAB61139.1.
U78084 mRNA. Translation: AAB53369.1.
AF084184 Genomic DNA. Translation: AAC33129.1.
AF084184 Genomic DNA. Translation: AAC33128.1.
AF017024 mRNA. Translation: AAD01610.1.
AF017025 mRNA. Translation: AAD01611.1.
AF017026 Genomic DNA. Translation: AAD01612.1.
AF093402 Genomic DNA. Translation: AAD52707.1.
AF093402 Genomic DNA. Translation: AAD52708.1.
AE014296 Genomic DNA. Translation: AAN12132.1.
AE014296 Genomic DNA. Translation: AAF51598.1.
AY061316 mRNA. Translation: AAL28864.1.
RefSeqiNP_001262110.1. NM_001275181.1. [O02194-2]
NP_001262111.1. NM_001275182.1. [O02194-1]
NP_524184.1. NM_079460.2. [O02194-1]
NP_730535.1. NM_168856.3. [O02194-2]
UniGeneiDm.3254.

Genome annotation databases

EnsemblMetazoaiFBtr0078192; FBpp0077850; FBgn0019947. [O02194-1]
FBtr0333479; FBpp0305666; FBgn0019947. [O02194-1]
GeneIDi40260.
KEGGidme:Dmel_CG18803.
UCSCiCG18803-RA. d. melanogaster. [O02194-1]

Keywords - Coding sequence diversityi

Alternative splicing

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
U77934 mRNA. Translation: AAB61139.1.
U78084 mRNA. Translation: AAB53369.1.
AF084184 Genomic DNA. Translation: AAC33129.1.
AF084184 Genomic DNA. Translation: AAC33128.1.
AF017024 mRNA. Translation: AAD01610.1.
AF017025 mRNA. Translation: AAD01611.1.
AF017026 Genomic DNA. Translation: AAD01612.1.
AF093402 Genomic DNA. Translation: AAD52707.1.
AF093402 Genomic DNA. Translation: AAD52708.1.
AE014296 Genomic DNA. Translation: AAN12132.1.
AE014296 Genomic DNA. Translation: AAF51598.1.
AY061316 mRNA. Translation: AAL28864.1.
RefSeqiNP_001262110.1. NM_001275181.1. [O02194-2]
NP_001262111.1. NM_001275182.1. [O02194-1]
NP_524184.1. NM_079460.2. [O02194-1]
NP_730535.1. NM_168856.3. [O02194-2]
UniGeneiDm.3254.

3D structure databases

ProteinModelPortaliO02194.
SMRiO02194. Positions 401-541.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi65518. 11 interactions.
DIPiDIP-1139N.
STRINGi7227.FBpp0077850.

Protein family/group databases

MEROPSiA22.014.

Proteomic databases

PaxDbiO02194.
PRIDEiO02194.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsemblMetazoaiFBtr0078192; FBpp0077850; FBgn0019947. [O02194-1]
FBtr0333479; FBpp0305666; FBgn0019947. [O02194-1]
GeneIDi40260.
KEGGidme:Dmel_CG18803.
UCSCiCG18803-RA. d. melanogaster. [O02194-1]

Organism-specific databases

CTDi40260.
FlyBaseiFBgn0019947. Psn.

Phylogenomic databases

eggNOGiKOG2736. Eukaryota.
ENOG410XPZD. LUCA.
GeneTreeiENSGT00390000016593.
InParanoidiO02194.
KOiK04505.
OMAiIEQHEEG.
OrthoDBiEOG7NGQBG.
PhylomeDBiO02194.

Enzyme and pathway databases

ReactomeiR-DME-1980148. Signaling by NOTCH3.
R-DME-1980150. Signaling by NOTCH4.
R-DME-3928665. EPH-ephrin mediated repulsion of cells.
SignaLinkiO02194.

Miscellaneous databases

GenomeRNAii40260.
PROiO02194.

Gene expression databases

BgeeiO02194.
ExpressionAtlasiO02194. differential.
GenevisibleiO02194. DM.

Family and domain databases

InterProiIPR001108. Peptidase_A22A.
IPR006639. Preselin/SPP.
[Graphical view]
PANTHERiPTHR10202. PTHR10202. 1 hit.
PfamiPF01080. Presenilin. 1 hit.
[Graphical view]
PRINTSiPR01072. PRESENILIN.
SMARTiSM00730. PSN. 1 hit.
[Graphical view]
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. Cited for: NUCLEOTIDE SEQUENCE [MRNA], ALTERNATIVE SPLICING, DEVELOPMENTAL STAGE.
    Tissue: Embryo.
  2. "Isolation and characterization of Drosophila presenilin homolog."
    Hong C.-S., Koo E.H.
    NeuroReport 8:665-668(1997) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 2), DEVELOPMENTAL STAGE.
    Strain: Canton-S.
    Tissue: Embryo and Head.
  3. "Characterization of Drosophila Presenilin and its colocalization with Notch during development."
    Ye Y., Fortini M.E.
    Mech. Dev. 79:199-211(1998) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA] (ISOFORMS 1 AND 2), TISSUE SPECIFICITY, DEVELOPMENTAL STAGE, SUBCELLULAR LOCATION, ALTERNATIVE SPLICING.
  4. "Neurogenic phenotypes and altered Notch processing in Drosophila Presenilin mutants."
    Ye Y., Lukinova N., Fortini M.E.
    Nature 398:525-529(1999) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE (ISOFORMS 1 AND 2), FUNCTION IN S3 CLEAVAGE OF NOTCH.
  5. "Identification of a Drosophila presenilin homologue: evidence of alternatively spliced forms."
    Marfany G., Del-Favero J., Valero R., De Jonghe C., Woodrow S., Hendriks L., Van Broeckhoven C., Gonzalez-Duarte R.
    J. Neurogenet. 12:41-54(1998) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA / MRNA], ALTERNATIVE SPLICING, DEVELOPMENTAL STAGE.
    Strain: Canton-S.
  6. "Drosophila presenilin is required for neuronal differentiation and affects notch subcellular localization and signaling."
    Guo Y., Livne-Bar I., Zhou L., Boulianne G.L.
    J. Neurosci. 19:8435-8442(1999) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA] (ISOFORMS 1 AND 2).
  7. "The genome sequence of Drosophila melanogaster."
    Adams M.D., Celniker S.E., Holt R.A., Evans C.A., Gocayne J.D., Amanatides P.G., Scherer S.E., Li P.W., Hoskins R.A., Galle R.F., George R.A., Lewis S.E., Richards S., Ashburner M., Henderson S.N., Sutton G.G., Wortman J.R., Yandell M.D.
    , Zhang Q., Chen L.X., Brandon R.C., Rogers Y.-H.C., Blazej R.G., Champe M., Pfeiffer B.D., Wan K.H., Doyle C., Baxter E.G., Helt G., Nelson C.R., Miklos G.L.G., Abril J.F., Agbayani A., An H.-J., Andrews-Pfannkoch C., Baldwin D., Ballew R.M., Basu A., Baxendale J., Bayraktaroglu L., Beasley E.M., Beeson K.Y., Benos P.V., Berman B.P., Bhandari D., Bolshakov S., Borkova D., Botchan M.R., Bouck J., Brokstein P., Brottier P., Burtis K.C., Busam D.A., Butler H., Cadieu E., Center A., Chandra I., Cherry J.M., Cawley S., Dahlke C., Davenport L.B., Davies P., de Pablos B., Delcher A., Deng Z., Mays A.D., Dew I., Dietz S.M., Dodson K., Doup L.E., Downes M., Dugan-Rocha S., Dunkov B.C., Dunn P., Durbin K.J., Evangelista C.C., Ferraz C., Ferriera S., Fleischmann W., Fosler C., Gabrielian A.E., Garg N.S., Gelbart W.M., Glasser K., Glodek A., Gong F., Gorrell J.H., Gu Z., Guan P., Harris M., Harris N.L., Harvey D.A., Heiman T.J., Hernandez J.R., Houck J., Hostin D., Houston K.A., Howland T.J., Wei M.-H., Ibegwam C., Jalali M., Kalush F., Karpen G.H., Ke Z., Kennison J.A., Ketchum K.A., Kimmel B.E., Kodira C.D., Kraft C.L., Kravitz S., Kulp D., Lai Z., Lasko P., Lei Y., Levitsky A.A., Li J.H., Li Z., Liang Y., Lin X., Liu X., Mattei B., McIntosh T.C., McLeod M.P., McPherson D., Merkulov G., Milshina N.V., Mobarry C., Morris J., Moshrefi A., Mount S.M., Moy M., Murphy B., Murphy L., Muzny D.M., Nelson D.L., Nelson D.R., Nelson K.A., Nixon K., Nusskern D.R., Pacleb J.M., Palazzolo M., Pittman G.S., Pan S., Pollard J., Puri V., Reese M.G., Reinert K., Remington K., Saunders R.D.C., Scheeler F., Shen H., Shue B.C., Siden-Kiamos I., Simpson M., Skupski M.P., Smith T.J., Spier E., Spradling A.C., Stapleton M., Strong R., Sun E., Svirskas R., Tector C., Turner R., Venter E., Wang A.H., Wang X., Wang Z.-Y., Wassarman D.A., Weinstock G.M., Weissenbach J., Williams S.M., Woodage T., Worley K.C., Wu D., Yang S., Yao Q.A., Ye J., Yeh R.-F., Zaveri J.S., Zhan M., Zhang G., Zhao Q., Zheng L., Zheng X.H., Zhong F.N., Zhong W., Zhou X., Zhu S.C., Zhu X., Smith H.O., Gibbs R.A., Myers E.W., Rubin G.M., Venter J.C.
    Science 287:2185-2195(2000) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    Strain: Berkeley.
  8. Cited for: GENOME REANNOTATION, ALTERNATIVE SPLICING.
    Strain: Berkeley.
  9. "A Drosophila full-length cDNA resource."
    Stapleton M., Carlson J.W., Brokstein P., Yu C., Champe M., George R.A., Guarin H., Kronmiller B., Pacleb J.M., Park S., Wan K.H., Rubin G.M., Celniker S.E.
    Genome Biol. 3:RESEARCH0080.1-RESEARCH0080.8(2002) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA] (ISOFORM 1).
    Strain: Berkeley.
    Tissue: Embryo.
  10. "Posttranslational modification and plasma membrane localization of the Drosophila melanogaster presenilin."
    Nowotny P., Gorski S.M., Han S.W., Philips K., Ray W.J., Nowotny V., Jones C.J., Clark R.F., Cagan R.L., Goate A.M.
    Mol. Cell. Neurosci. 15:88-98(2000) [PubMed] [Europe PMC] [Abstract]
    Cited for: ALTERNATIVE SPLICING (ISOFORM 3), CLEAVAGE.
  11. "Presenilin is required for activity and nuclear access of Notch in Drosophila."
    Struhl G., Greenwald I.
    Nature 398:522-525(1999) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION IN S3 CLEAVAGE OF NOTCH.
  12. "Identification of a novel family of putative methyltransferases that interact with human and Drosophila presenilins."
    Zhang S.X., Guo Y., Boulianne G.L.
    Gene 280:135-144(2001) [PubMed] [Europe PMC] [Abstract]
    Cited for: INTERACTION WITH METL.
  13. Cited for: FUNCTION IN THE GAMMA-SECRETASE COMPLEX, INTERACTION WITH PEN-2; APH-1 AND NCT.

Entry informationi

Entry nameiPSN_DROME
AccessioniPrimary (citable) accession number: O02194
Secondary accession number(s): O02395
, O76802, O96340, Q9TY80, Q9V3L9, Q9V3S1
Entry historyi
Integrated into UniProtKB/Swiss-Prot: July 15, 1999
Last sequence update: July 15, 1999
Last modified: June 8, 2016
This is version 144 of the entry and version 2 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programDrosophila annotation project

Miscellaneousi

Keywords - Technical termi

Complete proteome, Reference proteome

Documents

  1. Drosophila
    Drosophila: entries, gene names and cross-references to FlyBase
  2. Peptidase families
    Classification of peptidase families and list of entries
  3. 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.