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Protein

Adapter molecule crk

Gene

CRK

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

Functioni

Isoform Crk-II: Regulates cell adhesion, spreading and migration. Mediates attachment-induced MAPK8 activation, membrane ruffling and cell motility in a Rac-dependent manner. Involved in phagocytosis of apoptotic cells and cell motility via its interaction with DOCK1 and DOCK4. May regulate the EFNA5-EPHA3 signaling.4 Publications

Sites

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sitei237 – 2371Proline switchBy similarity

GO - Molecular functioni

  • ephrin receptor binding Source: UniProtKB
  • SH2 domain binding Source: UniProtKB

GO - Biological processi

Complete GO annotation...

Enzyme and pathway databases

ReactomeiR-HSA-170984. ARMS-mediated activation.
R-HSA-186763. Downstream signal transduction.
R-HSA-2029482. Regulation of actin dynamics for phagocytic cup formation.
R-HSA-372708. p130Cas linkage to MAPK signaling for integrins.
R-HSA-4420097. VEGFA-VEGFR2 Pathway.
R-HSA-8849471. PTK6 Regulates RHO GTPases, RAS GTPase and MAP kinases.
R-HSA-912631. Regulation of signaling by CBL.
SignaLinkiP46108.
SIGNORiP46108.

Names & Taxonomyi

Protein namesi
Recommended name:
Adapter molecule crk
Alternative name(s):
Proto-oncogene c-Crk
p38
Gene namesi
Name:CRK
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
Proteomesi
  • UP000005640 Componenti: Chromosome 17

Organism-specific databases

HGNCiHGNC:2362. CRK.

Subcellular locationi

  • Cytoplasm By similarity
  • Cell membrane By similarity

  • Note: Translocated to the plasma membrane upon cell adhesion.By similarity

GO - Cellular componenti

  • actin cytoskeleton Source: Ensembl
  • cytoplasm Source: UniProtKB
  • cytosol Source: Reactome
  • extracellular exosome Source: UniProtKB
  • nucleus Source: ProtInc
  • plasma membrane Source: UniProtKB-SubCell
Complete GO annotation...

Keywords - Cellular componenti

Cell membrane, Cytoplasm, Membrane

Pathology & Biotechi

Mutagenesis

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Mutagenesisi150 – 1501D → K: Abolishes interaction with DOCK1. 1 Publication
Mutagenesisi169 – 1691W → L: Abolishes interaction with DOCK5. 1 Publication

Keywords - Diseasei

Proto-oncogene

Organism-specific databases

PharmGKBiPA26880.

Chemistry

ChEMBLiCHEMBL5005.

Polymorphism and mutation databases

BioMutaiCRK.
DMDMi158939322.

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Initiator methionineiRemovedCombined sources
Chaini2 – 304303Adapter molecule crkPRO_0000079351Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei2 – 21N-acetylalanineCombined sources
Modified residuei40 – 401PhosphoserineCombined sources
Modified residuei41 – 411PhosphoserineCombined sources
Modified residuei74 – 741PhosphoserineCombined sources
Modified residuei83 – 831PhosphoserineCombined sources
Modified residuei108 – 1081PhosphotyrosineCombined sources
Modified residuei125 – 1251PhosphoserineCombined sources
Modified residuei221 – 2211Phosphotyrosine; by ABL11 Publication
Modified residuei239 – 2391PhosphotyrosineCombined sources
Isoform Crk-I (identifier: P46108-2)
Modified residuei194 – 1941PhosphoserineCombined sources

Post-translational modificationi

Phosphorylation of Crk-II (40 kDa) gives rise to a 42 kDa form. Isoform Crk-II is phosphorylated by KIT.
Phosphorylated on Tyr-221 upon cell adhesion. Results in the negative regulation of the association with SH2- and SH3-binding partners, possibly by the formation of an intramolecular interaction of phosphorylated Tyr-221 with the SH2 domain. This leads finally to the down-regulation of the Crk signaling pathway.1 Publication
Proline isomerization at Pro-237 by PPIA acts as a switch between two conformations: an autoinhibitory conformation in the cis form, where the tandem SH3 domains interact intramolecularly, and an activated conformation in the trans form.By similarity

Keywords - PTMi

Acetylation, Phosphoprotein

Proteomic databases

EPDiP46108.
MaxQBiP46108.
PaxDbiP46108.
PeptideAtlasiP46108.
PRIDEiP46108.
TopDownProteomicsiP46108-1. [P46108-1]
P46108-2. [P46108-2]

2D gel databases

REPRODUCTION-2DPAGEIPI00399054.
SWISS-2DPAGEP46108.

PTM databases

iPTMnetiP46108.
PhosphoSiteiP46108.

Expressioni

Gene expression databases

BgeeiENSG00000167193.
CleanExiHS_CRK.
ExpressionAtlasiP46108. baseline and differential.
GenevisibleiP46108. HS.

Organism-specific databases

HPAiCAB010485.
HPA068087.

Interactioni

Subunit structurei

Interacts with ABL1, C3G, DOCK3, DOCK5, MAP4K1, MAPK8 and SOS via its first SH3 domain. Interacts (via SH2 domain) with BCAR1, CBL, CBLB, PXN, IRS4 and GAB1 upon stimulus-induced tyrosine phosphorylation. Interacts (via SH2 domain) with several tyrosine-phosphorylated growth factor receptors such as EGFR and INSR. Interacts with FLT1 (tyrosine-phosphorylated). Interacts with DOCK1 and DOCK4. Interacts with SHB. Interacts with PEAK1. Interacts with FASLG. Isoform Crk-II interacts with KIT. Interacts with EPHA3; upon activation of EPHA3 by the ligand EFNA5 and EPHA3 tyrosine kinase activity-dependent. Interacts with EPHA3 (phosphorylated); mediates EFNA5-EPHA3 signaling through RHOA GTPase activation. Interacts with FLT4 (tyrosine-phosphorylated). Isoform Crk-II (via SH2 domain) interacts with PDGFRA (tyrosine phosphorylated) and PDGFRB (tyrosine phosphorylated). Part of a collagen stimulated complex involved in cell migration composed of CDC42, CRK, TNK2 and p130cas/BCAR1. Interacts (via SH2 domain) with the 'Tyr-9' phosphorylated form of PDPK1. Interacts with CBLC. Found in a complex with ABL1, ABL2, CRK and UNC119; leading to the inhibition of CRK phosphorylation by ABL kinases.16 Publications

Binary interactionsi

WithEntry#Exp.IntActNotes
ABL1P005192EBI-886,EBI-375543
ABL2P426845EBI-886,EBI-1102694
ARHGEF11O150852EBI-886,EBI-311099
ASAP1Q9ULH12EBI-886,EBI-346622
ASB9Q96DX52EBI-886,EBI-745641
ATXN1P542533EBI-886,EBI-930964
BCAR1P569455EBI-886,EBI-702093
CBLP226818EBI-886,EBI-518228
CBLBQ131914EBI-886,EBI-744027
EGFRP005333EBI-886,EBI-297353
ERBB3P218602EBI-886,EBI-720706
FGFR1P113622EBI-886,EBI-1028277
FLNAP213333EBI-886,EBI-350432
FLNCQ143152EBI-886,EBI-489954
GAB1Q134802EBI-886,EBI-517684
IRS4O146548EBI-886,EBI-356594
KDRP359682EBI-886,EBI-1005487
KITP107214EBI-886,EBI-1379503
MAP4K1Q929183EBI-886,EBI-881
MAP4K5Q9Y4K45EBI-886,EBI-1279
MAPK8P459832EBI-886,EBI-286483
OGNP207742EBI-886,EBI-1753690
PDGFRAP162344EBI-886,EBI-2861522
PIK3R1P279862EBI-886,EBI-79464
PIK3R3Q925693EBI-886,EBI-79893
PTK2Q053973EBI-886,EBI-702142
PTPN4P290743EBI-886,EBI-710431
RAPGEF1Q139053EBI-886,EBI-976876
RIN3Q8TB242EBI-886,EBI-1570523
SAXO1Q8IYX73EBI-886,EBI-3957636
SHANK2Q9UPX82EBI-886,EBI-1570571
SHC1P293533EBI-886,EBI-78835
SNX3O604932EBI-886,EBI-727209
SOS1Q078893EBI-886,EBI-297487
SOS2Q078902EBI-886,EBI-298181
TERF2IPQ9NYB02EBI-886,EBI-750109

GO - Molecular functioni

  • ephrin receptor binding Source: UniProtKB
  • SH2 domain binding Source: UniProtKB

Protein-protein interaction databases

BioGridi107788. 252 interactions.
DIPiDIP-199N.
IntActiP46108. 272 interactions.
MINTiMINT-1208745.
STRINGi9606.ENSP00000300574.

Structurei

Secondary structure

1
304
Legend: HelixTurnBeta strand
Show more details
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Beta strandi7 – 137Combined sources
Beta strandi14 – 163Combined sources
Helixi20 – 278Combined sources
Beta strandi30 – 334Combined sources
Beta strandi34 – 396Combined sources
Beta strandi41 – 433Combined sources
Beta strandi46 – 527Combined sources
Beta strandi54 – 563Combined sources
Beta strandi57 – 637Combined sources
Beta strandi66 – 694Combined sources
Beta strandi70 – 778Combined sources
Turni78 – 803Combined sources
Beta strandi87 – 893Combined sources
Beta strandi92 – 965Combined sources
Helixi97 – 10610Combined sources
Beta strandi109 – 1124Combined sources
Beta strandi116 – 1183Combined sources
Beta strandi120 – 1234Combined sources
Helixi126 – 1283Combined sources
Beta strandi135 – 1384Combined sources
Beta strandi146 – 1505Combined sources
Beta strandi158 – 1669Combined sources
Beta strandi167 – 1737Combined sources
Beta strandi179 – 1835Combined sources
Helixi184 – 1863Combined sources
Beta strandi187 – 1893Combined sources
Beta strandi208 – 2103Combined sources
Beta strandi224 – 2274Combined sources
Beta strandi229 – 2313Combined sources
Beta strandi239 – 2424Combined sources
Beta strandi253 – 2553Combined sources
Beta strandi260 – 26910Combined sources
Beta strandi273 – 2797Combined sources
Beta strandi282 – 2876Combined sources
Helixi288 – 2903Combined sources

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
1JU5NMR-A12-120[»]
2DVJNMR-A1-228[»]
2EYVNMR-A6-124[»]
2EYWNMR-A125-198[»]
2EYXNMR-A232-298[»]
2EYYNMR-A1-204[»]
2EYZNMR-A1-304[»]
2MS4NMR-B216-224[»]
DisProtiDP00748.
ProteinModelPortaliP46108.
SMRiP46108. Positions 1-304.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiP46108.

Family & Domainsi

Domains and Repeats

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Domaini13 – 118106SH2PROSITE-ProRule annotationAdd
BLAST
Domaini132 – 19261SH3 1PROSITE-ProRule annotationAdd
BLAST
Domaini237 – 29660SH3 2PROSITE-ProRule annotationAdd
BLAST

Domaini

The C-terminal SH3 domain function as a negative modulator for transformation and the N-terminal SH3 domain appears to function as a positive regulator for transformation.By similarity
The SH2 domain mediates interaction with tyrosine phosphorylated proteins. Mediates interaction with SHB.

Sequence similaritiesi

Belongs to the CRK family.Curated
Contains 1 SH2 domain.PROSITE-ProRule annotation
Contains 2 SH3 domains.PROSITE-ProRule annotation

Keywords - Domaini

Repeat, SH2 domain, SH3 domain

Phylogenomic databases

eggNOGiKOG4792. Eukaryota.
ENOG4110574. LUCA.
GeneTreeiENSGT00820000127055.
HOGENOMiHOG000236288.
HOVERGENiHBG105616.
InParanoidiP46108.
KOiK04438.
OMAiNQDSSHP.
OrthoDBiEOG091G0JPQ.
PhylomeDBiP46108.
TreeFamiTF321436.

Family and domain databases

Gene3Di3.30.505.10. 1 hit.
InterProiIPR000980. SH2.
IPR011511. SH3_2.
IPR001452. SH3_domain.
[Graphical view]
PfamiPF00017. SH2. 1 hit.
PF00018. SH3_1. 1 hit.
PF07653. SH3_2. 1 hit.
[Graphical view]
PRINTSiPR00401. SH2DOMAIN.
PR00452. SH3DOMAIN.
SMARTiSM00252. SH2. 1 hit.
SM00326. SH3. 2 hits.
[Graphical view]
SUPFAMiSSF50044. SSF50044. 3 hits.
SSF55550. SSF55550. 2 hits.
PROSITEiPS50001. SH2. 1 hit.
PS50002. SH3. 1 hit.
[Graphical view]

Sequences (2)i

Sequence statusi: Complete.

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

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

Isoform Crk-II (identifier: P46108-1) [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
MAGNFDSEER SSWYWGRLSR QEAVALLQGQ RHGVFLVRDS STSPGDYVLS
60 70 80 90 100
VSENSRVSHY IINSSGPRPP VPPSPAQPPP GVSPSRLRIG DQEFDSLPAL
110 120 130 140 150
LEFYKIHYLD TTTLIEPVSR SRQGSGVILR QEEAEYVRAL FDFNGNDEED
160 170 180 190 200
LPFKKGDILR IRDKPEEQWW NAEDSEGKRG MIPVPYVEKY RPASASVSAL
210 220 230 240 250
IGGNQEGSHP QPLGGPEPGP YAQPSVNTPL PNLQNGPIYA RVIQKRVPNA
260 270 280 290 300
YDKTALALEV GELVKVTKIN VSGQWEGECN GKRGHFPFTH VRLLDQQNPD

EDFS
Length:304
Mass (Da):33,831
Last modified:July 24, 2007 - v2
Checksum:i4CFBFB65BFC2E265
GO
Isoform Crk-I (identifier: P46108-2) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     204-204: N → R
     205-304: Missing.

Show »
Length:204
Mass (Da):22,906
Checksum:iB4C5BF23887B6B80
GO

Experimental Info

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sequence conflicti109 – 1091L → W in BAA01505 (PubMed:1630456).Curated
Sequence conflicti109 – 1091L → W in AAB28213 (PubMed:8378094).Curated
Sequence conflicti215 – 2151G → P in BAA01505 (PubMed:1630456).Curated
Sequence conflicti215 – 2151G → P in AAB28213 (PubMed:8378094).Curated
Sequence conflicti278 – 2781E → G in BAA01505 (PubMed:1630456).Curated
Sequence conflicti278 – 2781E → G in AAB28213 (PubMed:8378094).Curated

Alternative sequence

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Alternative sequencei204 – 2041N → R in isoform Crk-I. 2 PublicationsVSP_041153
Alternative sequencei205 – 304100Missing in isoform Crk-I. 2 PublicationsVSP_041154Add
BLAST

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
D10656 mRNA. Translation: BAA01505.1.
S65701 Genomic DNA. Translation: AAB28213.1.
BT007277 mRNA. Translation: AAP35941.1.
EU332838 Genomic DNA. Translation: ABY87527.1.
AK291060 mRNA. Translation: BAF83749.1.
AC032044 Genomic DNA. No translation available.
AC100748 Genomic DNA. No translation available.
CH471108 Genomic DNA. Translation: EAW90621.1.
CH471108 Genomic DNA. Translation: EAW90624.1.
CH471108 Genomic DNA. Translation: EAW90625.1.
BC001718 mRNA. Translation: AAH01718.1.
BC008506 mRNA. Translation: AAH08506.1.
BC009837 mRNA. Translation: AAH09837.1.
CCDSiCCDS11002.1. [P46108-1]
CCDS45561.1. [P46108-2]
PIRiA45022.
RefSeqiNP_005197.3. NM_005206.4. [P46108-2]
NP_058431.2. NM_016823.3. [P46108-1]
UniGeneiHs.461896.

Genome annotation databases

EnsembliENST00000300574; ENSP00000300574; ENSG00000167193. [P46108-1]
ENST00000398970; ENSP00000381942; ENSG00000167193. [P46108-2]
GeneIDi1398.
KEGGihsa:1398.
UCSCiuc002fsl.4. human. [P46108-1]

Keywords - Coding sequence diversityi

Alternative splicing

Cross-referencesi

Web resourcesi

Atlas of Genetics and Cytogenetics in Oncology and Haematology

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
D10656 mRNA. Translation: BAA01505.1.
S65701 Genomic DNA. Translation: AAB28213.1.
BT007277 mRNA. Translation: AAP35941.1.
EU332838 Genomic DNA. Translation: ABY87527.1.
AK291060 mRNA. Translation: BAF83749.1.
AC032044 Genomic DNA. No translation available.
AC100748 Genomic DNA. No translation available.
CH471108 Genomic DNA. Translation: EAW90621.1.
CH471108 Genomic DNA. Translation: EAW90624.1.
CH471108 Genomic DNA. Translation: EAW90625.1.
BC001718 mRNA. Translation: AAH01718.1.
BC008506 mRNA. Translation: AAH08506.1.
BC009837 mRNA. Translation: AAH09837.1.
CCDSiCCDS11002.1. [P46108-1]
CCDS45561.1. [P46108-2]
PIRiA45022.
RefSeqiNP_005197.3. NM_005206.4. [P46108-2]
NP_058431.2. NM_016823.3. [P46108-1]
UniGeneiHs.461896.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
1JU5NMR-A12-120[»]
2DVJNMR-A1-228[»]
2EYVNMR-A6-124[»]
2EYWNMR-A125-198[»]
2EYXNMR-A232-298[»]
2EYYNMR-A1-204[»]
2EYZNMR-A1-304[»]
2MS4NMR-B216-224[»]
DisProtiDP00748.
ProteinModelPortaliP46108.
SMRiP46108. Positions 1-304.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi107788. 252 interactions.
DIPiDIP-199N.
IntActiP46108. 272 interactions.
MINTiMINT-1208745.
STRINGi9606.ENSP00000300574.

Chemistry

ChEMBLiCHEMBL5005.

PTM databases

iPTMnetiP46108.
PhosphoSiteiP46108.

Polymorphism and mutation databases

BioMutaiCRK.
DMDMi158939322.

2D gel databases

REPRODUCTION-2DPAGEIPI00399054.
SWISS-2DPAGEP46108.

Proteomic databases

EPDiP46108.
MaxQBiP46108.
PaxDbiP46108.
PeptideAtlasiP46108.
PRIDEiP46108.
TopDownProteomicsiP46108-1. [P46108-1]
P46108-2. [P46108-2]

Protocols and materials databases

DNASUi1398.
Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000300574; ENSP00000300574; ENSG00000167193. [P46108-1]
ENST00000398970; ENSP00000381942; ENSG00000167193. [P46108-2]
GeneIDi1398.
KEGGihsa:1398.
UCSCiuc002fsl.4. human. [P46108-1]

Organism-specific databases

CTDi1398.
GeneCardsiCRK.
HGNCiHGNC:2362. CRK.
HPAiCAB010485.
HPA068087.
MIMi164762. gene.
neXtProtiNX_P46108.
PharmGKBiPA26880.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiKOG4792. Eukaryota.
ENOG4110574. LUCA.
GeneTreeiENSGT00820000127055.
HOGENOMiHOG000236288.
HOVERGENiHBG105616.
InParanoidiP46108.
KOiK04438.
OMAiNQDSSHP.
OrthoDBiEOG091G0JPQ.
PhylomeDBiP46108.
TreeFamiTF321436.

Enzyme and pathway databases

ReactomeiR-HSA-170984. ARMS-mediated activation.
R-HSA-186763. Downstream signal transduction.
R-HSA-2029482. Regulation of actin dynamics for phagocytic cup formation.
R-HSA-372708. p130Cas linkage to MAPK signaling for integrins.
R-HSA-4420097. VEGFA-VEGFR2 Pathway.
R-HSA-8849471. PTK6 Regulates RHO GTPases, RAS GTPase and MAP kinases.
R-HSA-912631. Regulation of signaling by CBL.
SignaLinkiP46108.
SIGNORiP46108.

Miscellaneous databases

ChiTaRSiCRK. human.
EvolutionaryTraceiP46108.
GeneWikiiCRK_(gene).
GenomeRNAii1398.
PROiP46108.
SOURCEiSearch...

Gene expression databases

BgeeiENSG00000167193.
CleanExiHS_CRK.
ExpressionAtlasiP46108. baseline and differential.
GenevisibleiP46108. HS.

Family and domain databases

Gene3Di3.30.505.10. 1 hit.
InterProiIPR000980. SH2.
IPR011511. SH3_2.
IPR001452. SH3_domain.
[Graphical view]
PfamiPF00017. SH2. 1 hit.
PF00018. SH3_1. 1 hit.
PF07653. SH3_2. 1 hit.
[Graphical view]
PRINTSiPR00401. SH2DOMAIN.
PR00452. SH3DOMAIN.
SMARTiSM00252. SH2. 1 hit.
SM00326. SH3. 2 hits.
[Graphical view]
SUPFAMiSSF50044. SSF50044. 3 hits.
SSF55550. SSF55550. 2 hits.
PROSITEiPS50001. SH2. 1 hit.
PS50002. SH3. 1 hit.
[Graphical view]
ProtoNetiSearch...

Entry informationi

Entry nameiCRK_HUMAN
AccessioniPrimary (citable) accession number: P46108
Secondary accession number(s): A8MWE8
, B0LPE8, D3DTH6, Q96GA9, Q96HJ0
Entry historyi
Integrated into UniProtKB/Swiss-Prot: November 1, 1995
Last sequence update: July 24, 2007
Last modified: September 7, 2016
This is version 178 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

Keywords - Technical termi

3D-structure, Complete proteome, Reference proteome

Documents

  1. Human chromosome 17
    Human chromosome 17: 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.