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Protein

Small nuclear ribonucleoprotein F

Gene

SNRPF

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

Functioni

Core component of the spliceosomal U1, U2, U4 and U5 small nuclear ribonucleoproteins (snRNPs), the building blocks of the spliceosome. Thereby, plays an important role in the splicing of cellular pre-mRNAs. Most spliceosomal snRNPs contain a common set of Sm proteins SNRPB, SNRPD1, SNRPD2, SNRPD3, SNRPE, SNRPF and SNRPG that assemble in an heptameric protein ring on the Sm site of the small nuclear RNA to form the core snRNP. As part of the U7 snRNP it is involved in histone 3'-end processing.2 Publications

GO - Molecular functioni

  1. RNA binding Source: UniProtKB

GO - Biological processi

  1. gene expression Source: Reactome
  2. histone mRNA metabolic process Source: Reactome
  3. mRNA 3'-end processing Source: Reactome
  4. mRNA splicing, via spliceosome Source: UniProtKB
  5. ncRNA metabolic process Source: Reactome
  6. RNA splicing Source: UniProtKB
  7. spliceosomal snRNP assembly Source: UniProtKB
  8. termination of RNA polymerase II transcription Source: Reactome
  9. transcription from RNA polymerase II promoter Source: Reactome
Complete GO annotation...

Keywords - Molecular functioni

Ribonucleoprotein

Keywords - Biological processi

mRNA processing, mRNA splicing

Keywords - Ligandi

RNA-binding

Enzyme and pathway databases

ReactomeiREACT_11066. snRNP Assembly.
REACT_1364. SLBP Dependent Processing of Replication-Dependent Histone Pre-mRNAs.
REACT_1753. mRNA Splicing - Minor Pathway.
REACT_185. SLBP independent Processing of Histone Pre-mRNAs.
REACT_387. Cleavage of Growing Transcript in the Termination Region.
REACT_467. mRNA Splicing - Major Pathway.

Names & Taxonomyi

Protein namesi
Recommended name:
Small nuclear ribonucleoprotein F
Short name:
snRNP-F
Alternative name(s):
Sm protein F
Short name:
Sm-F
Short name:
SmF
Gene namesi
Name:SNRPF
Synonyms:PBSCF
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
ProteomesiUP000005640 Componenti: Chromosome 12

Organism-specific databases

HGNCiHGNC:11162. SNRPF.

Subcellular locationi

Cytoplasmcytosol 1 Publication. Nucleus 1 Publication
Note: SMN-mediated assembly into core snRNPs occurs in the cytosol before SMN-mediated transport to the nucleus to be included in spliceosomes.

GO - Cellular componenti

  1. catalytic step 2 spliceosome Source: UniProtKB
  2. cytosol Source: UniProtKB
  3. methylosome Source: UniProtKB
  4. nucleoplasm Source: Reactome
  5. pICln-Sm protein complex Source: UniProtKB
  6. small nuclear ribonucleoprotein complex Source: UniProtKB
  7. SMN-Sm protein complex Source: UniProtKB
  8. spliceosomal complex Source: UniProtKB
  9. U12-type spliceosomal complex Source: UniProtKB
  10. U1 snRNP Source: UniProtKB
  11. U4 snRNP Source: UniProtKB
  12. U7 snRNP Source: UniProtKB
Complete GO annotation...

Keywords - Cellular componenti

Cytoplasm, Nucleus, Spliceosome

Pathology & Biotechi

Organism-specific databases

PharmGKBiPA36003.

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Initiator methioninei1 – 11Removed1 Publication
Chaini2 – 8685Small nuclear ribonucleoprotein FPRO_0000125536Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei2 – 21N-acetylserine1 Publication

Keywords - PTMi

Acetylation

Proteomic databases

MaxQBiP62306.
PaxDbiP62306.
PeptideAtlasiP62306.
PRIDEiP62306.

PTM databases

PhosphoSiteiP62306.

Miscellaneous databases

PMAP-CutDBP62306.

Expressioni

Gene expression databases

BgeeiP62306.
CleanExiHS_SNRPF.
ExpressionAtlasiP62306. baseline and differential.
GenevestigatoriP62306.

Interactioni

Subunit structurei

U1 snRNP is for instance composed of the 7 core Sm proteins SNRPB, SNRPD1, SNRPD2, SNRPD3, SNRPE, SNRPF and SNRPG that assemble in an heptameric protein ring on the Sm site of the small nuclear RNA to form the core snRNP, and at least three U1 snRNP-specific proteins SNRNP70/U1-70K, SNRPA/U1-A and SNRPC/U1-C. Component of the U11/U12 snRNPs that are part of the U12-type spliceosome. Component of the heptameric ring U7 snRNP complex, or U7 Sm protein core complex, at least composed of LSM10, LSM11, SNRPB, SNRPD3, SNRPE, SNRPF, SNRPG and U7 snRNA. Part of the SMN-Sm complex that contains SMN1, GEMIN2/SIP1, DDX20/GEMIN3, GEMIN4, GEMIN5, GEMIN6, GEMIN7, GEMIN8, STRAP/UNRIP and the Sm proteins SNRPB, SNRPD1, SNRPD2, SNRPD3, SNRPE, SNRPF and SNRPG; catalyzes core snRNPs assembly. Forms a 6S pICln-Sm complex composed of CLNS1A/pICln, SNRPD1, SNRPD2, SNRPE, SNRPF and SNRPG; ring-like structure where CLNS1A/pICln mimics additional Sm proteins and which is unable to assemble into the core snRNP.5 Publications

Binary interactionsi

WithEntry#Exp.IntActNotes
CLNS1AP541054EBI-356900,EBI-724693
SNRPEP623044EBI-356900,EBI-348082

Protein-protein interaction databases

BioGridi112520. 71 interactions.
DIPiDIP-31221N.
IntActiP62306. 28 interactions.
MINTiMINT-1137229.
STRINGi9606.ENSP00000266735.

Structurei

Secondary structure

1
86
Legend: HelixTurnBeta strand
Show more details
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Helixi7 – 148Combined sources
Beta strandi17 – 237Combined sources
Beta strandi28 – 369Combined sources
Beta strandi42 – 5110Combined sources
Beta strandi54 – 6411Combined sources
Helixi66 – 683Combined sources
Beta strandi69 – 746Combined sources

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
3CW1X-ray5.491/2/F/Z1-86[»]
3PGWX-ray4.40F/I1-86[»]
3S6NX-ray2.50F1-86[»]
4F7UX-ray1.90F/I1-86[»]
4PJOX-ray3.30F/T/f/t1-75[»]
4V98X-ray3.10AD/AL/AT/Ab/Aj/Ar/Az/BD/BL/BT/Bb/Bj/Br/Bz/CD/CL/CT/Cb/Cj/Cr1-86[»]
4WZJX-ray3.60AF/AM/AT/BF/BM/BT/CF/CM/CT/DF/DM/DT1-86[»]
ProteinModelPortaliP62306.
SMRiP62306. Positions 3-76.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiP62306.

Family & Domainsi

Sequence similaritiesi

Phylogenomic databases

eggNOGiCOG1958.
GeneTreeiENSGT00730000110856.
HOVERGENiHBG052369.
InParanoidiP62306.
KOiK11098.
OMAiSTDGYMN.
OrthoDBiEOG7HXCTK.
PhylomeDBiP62306.
TreeFamiTF314481.

Family and domain databases

InterProiIPR016487. Lsm6/sSmF.
IPR010920. LSM_dom.
IPR001163. Ribonucl_LSM.
IPR006649. Ribonucl_LSM_euk/arc.
[Graphical view]
PfamiPF01423. LSM. 1 hit.
[Graphical view]
PIRSFiPIRSF006609. snRNP_SmF. 1 hit.
SMARTiSM00651. Sm. 1 hit.
[Graphical view]
SUPFAMiSSF50182. SSF50182. 1 hit.

Sequencei

Sequence statusi: Complete.

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

P62306-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MSLPLNPKPF LNGLTGKPVM VKLKWGMEYK GYLVSVDGYM NMQLANTEEY
60 70 80
IDGALSGHLG EVLIRCNNVL YIRGVEEEEE DGEMRE
Length:86
Mass (Da):9,725
Last modified:July 4, 2004 - v1
Checksum:i416B88D575DAE58A
GO

Experimental Info

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sequence conflicti86 – 861E → D in CAG33032 (Ref. 2) Curated

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
X85372 mRNA. Translation: CAA59688.1.
CR456751 mRNA. Translation: CAG33032.1.
AK311752 mRNA. Translation: BAG34695.1.
CH471054 Genomic DNA. Translation: EAW97548.1.
BC002505 mRNA. Translation: AAH02505.3.
BC063397 mRNA. Translation: AAH63397.2.
BC128452 mRNA. Translation: AAI28453.1.
BC128453 mRNA. Translation: AAI28454.1.
CCDSiCCDS9055.1.
PIRiS55053.
RefSeqiNP_003086.1. NM_003095.2.
UniGeneiHs.105465.

Genome annotation databases

EnsembliENST00000266735; ENSP00000266735; ENSG00000139343.
GeneIDi6636.
KEGGihsa:6636.
UCSCiuc001tej.3. human.

Polymorphism databases

DMDMi61237391.

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
X85372 mRNA. Translation: CAA59688.1.
CR456751 mRNA. Translation: CAG33032.1.
AK311752 mRNA. Translation: BAG34695.1.
CH471054 Genomic DNA. Translation: EAW97548.1.
BC002505 mRNA. Translation: AAH02505.3.
BC063397 mRNA. Translation: AAH63397.2.
BC128452 mRNA. Translation: AAI28453.1.
BC128453 mRNA. Translation: AAI28454.1.
CCDSiCCDS9055.1.
PIRiS55053.
RefSeqiNP_003086.1. NM_003095.2.
UniGeneiHs.105465.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
3CW1X-ray5.491/2/F/Z1-86[»]
3PGWX-ray4.40F/I1-86[»]
3S6NX-ray2.50F1-86[»]
4F7UX-ray1.90F/I1-86[»]
4PJOX-ray3.30F/T/f/t1-75[»]
4V98X-ray3.10AD/AL/AT/Ab/Aj/Ar/Az/BD/BL/BT/Bb/Bj/Br/Bz/CD/CL/CT/Cb/Cj/Cr1-86[»]
4WZJX-ray3.60AF/AM/AT/BF/BM/BT/CF/CM/CT/DF/DM/DT1-86[»]
ProteinModelPortaliP62306.
SMRiP62306. Positions 3-76.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi112520. 71 interactions.
DIPiDIP-31221N.
IntActiP62306. 28 interactions.
MINTiMINT-1137229.
STRINGi9606.ENSP00000266735.

PTM databases

PhosphoSiteiP62306.

Polymorphism databases

DMDMi61237391.

Proteomic databases

MaxQBiP62306.
PaxDbiP62306.
PeptideAtlasiP62306.
PRIDEiP62306.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000266735; ENSP00000266735; ENSG00000139343.
GeneIDi6636.
KEGGihsa:6636.
UCSCiuc001tej.3. human.

Organism-specific databases

CTDi6636.
GeneCardsiGC12P096252.
HGNCiHGNC:11162. SNRPF.
MIMi603541. gene.
neXtProtiNX_P62306.
PharmGKBiPA36003.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiCOG1958.
GeneTreeiENSGT00730000110856.
HOVERGENiHBG052369.
InParanoidiP62306.
KOiK11098.
OMAiSTDGYMN.
OrthoDBiEOG7HXCTK.
PhylomeDBiP62306.
TreeFamiTF314481.

Enzyme and pathway databases

ReactomeiREACT_11066. snRNP Assembly.
REACT_1364. SLBP Dependent Processing of Replication-Dependent Histone Pre-mRNAs.
REACT_1753. mRNA Splicing - Minor Pathway.
REACT_185. SLBP independent Processing of Histone Pre-mRNAs.
REACT_387. Cleavage of Growing Transcript in the Termination Region.
REACT_467. mRNA Splicing - Major Pathway.

Miscellaneous databases

ChiTaRSiSNRPF. human.
EvolutionaryTraceiP62306.
GeneWikiiSmall_nuclear_ribonucleoprotein_polypeptide_F.
GenomeRNAii6636.
NextBioi25853.
PMAP-CutDBP62306.
PROiP62306.
SOURCEiSearch...

Gene expression databases

BgeeiP62306.
CleanExiHS_SNRPF.
ExpressionAtlasiP62306. baseline and differential.
GenevestigatoriP62306.

Family and domain databases

InterProiIPR016487. Lsm6/sSmF.
IPR010920. LSM_dom.
IPR001163. Ribonucl_LSM.
IPR006649. Ribonucl_LSM_euk/arc.
[Graphical view]
PfamiPF01423. LSM. 1 hit.
[Graphical view]
PIRSFiPIRSF006609. snRNP_SmF. 1 hit.
SMARTiSM00651. Sm. 1 hit.
[Graphical view]
SUPFAMiSSF50182. SSF50182. 1 hit.
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "snRNP Sm proteins share two evolutionarily conserved sequence motifs which are involved in Sm protein-protein interactions."
    Hermann H., Fabrizio P., Raker V.A., Foulaki K., Hornig H., Brahms H., Luehrmann R.
    EMBO J. 14:2076-2088(1994) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA].
    Tissue: Cervix carcinoma.
  2. "Cloning of human full open reading frames in Gateway(TM) system entry vector (pDONR201)."
    Ebert L., Schick M., Neubert P., Schatten R., Henze S., Korn B.
    Submitted (MAY-2004) to the EMBL/GenBank/DDBJ databases
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA].
  3. "Complete sequencing and characterization of 21,243 full-length human cDNAs."
    Ota T., Suzuki Y., Nishikawa T., Otsuki T., Sugiyama T., Irie R., Wakamatsu A., Hayashi K., Sato H., Nagai K., Kimura K., Makita H., Sekine M., Obayashi M., Nishi T., Shibahara T., Tanaka T., Ishii S.
    , Yamamoto J., Saito K., Kawai Y., Isono Y., Nakamura Y., Nagahari K., Murakami K., Yasuda T., Iwayanagi T., Wagatsuma M., Shiratori A., Sudo H., Hosoiri T., Kaku Y., Kodaira H., Kondo H., Sugawara M., Takahashi M., Kanda K., Yokoi T., Furuya T., Kikkawa E., Omura Y., Abe K., Kamihara K., Katsuta N., Sato K., Tanikawa M., Yamazaki M., Ninomiya K., Ishibashi T., Yamashita H., Murakawa K., Fujimori K., Tanai H., Kimata M., Watanabe M., Hiraoka S., Chiba Y., Ishida S., Ono Y., Takiguchi S., Watanabe S., Yosida M., Hotuta T., Kusano J., Kanehori K., Takahashi-Fujii A., Hara H., Tanase T.-O., Nomura Y., Togiya S., Komai F., Hara R., Takeuchi K., Arita M., Imose N., Musashino K., Yuuki H., Oshima A., Sasaki N., Aotsuka S., Yoshikawa Y., Matsunawa H., Ichihara T., Shiohata N., Sano S., Moriya S., Momiyama H., Satoh N., Takami S., Terashima Y., Suzuki O., Nakagawa S., Senoh A., Mizoguchi H., Goto Y., Shimizu F., Wakebe H., Hishigaki H., Watanabe T., Sugiyama A., Takemoto M., Kawakami B., Yamazaki M., Watanabe K., Kumagai A., Itakura S., Fukuzumi Y., Fujimori Y., Komiyama M., Tashiro H., Tanigami A., Fujiwara T., Ono T., Yamada K., Fujii Y., Ozaki K., Hirao M., Ohmori Y., Kawabata A., Hikiji T., Kobatake N., Inagaki H., Ikema Y., Okamoto S., Okitani R., Kawakami T., Noguchi S., Itoh T., Shigeta K., Senba T., Matsumura K., Nakajima Y., Mizuno T., Morinaga M., Sasaki M., Togashi T., Oyama M., Hata H., Watanabe M., Komatsu T., Mizushima-Sugano J., Satoh T., Shirai Y., Takahashi Y., Nakagawa K., Okumura K., Nagase T., Nomura N., Kikuchi H., Masuho Y., Yamashita R., Nakai K., Yada T., Nakamura Y., Ohara O., Isogai T., Sugano S.
    Nat. Genet. 36:40-45(2003) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA].
    Tissue: Amygdala.
  4. Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
  5. "The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC)."
    The MGC Project Team
    Genome Res. 14:2121-2127(2003) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA].
    Tissue: Colon.
  6. Bienvenut W.V., Lilla S., von Kriegsheim A., Lempens A., Kolch W.
    Submitted (NOV-2008) to UniProtKB
    Cited for: PROTEIN SEQUENCE OF 2-22 AND 66-86, CLEAVAGE OF INITIATOR METHIONINE, ACETYLATION AT SER-2, IDENTIFICATION BY MASS SPECTROMETRY.
    Tissue: Ovarian carcinoma.
  7. "Purified U7 snRNPs lack the Sm proteins D1 and D2 but contain Lsm10, a new 14 kDa Sm D1-like protein."
    Pillai R.S., Will C.L., Luehrmann R., Schuemperli D., Mueller B.
    EMBO J. 20:5470-5479(2000) [PubMed] [Europe PMC] [Abstract]
    Cited for: IDENTIFICATION IN THE U7 SNRNP COMPLEX.
  8. "Purification and characterization of native spliceosomes suitable for three-dimensional structural analysis."
    Jurica M.S., Licklider L.J., Gygi S.P., Grigorieff N., Moore M.J.
    RNA 8:426-439(2001) [PubMed] [Europe PMC] [Abstract]
    Cited for: IDENTIFICATION BY MASS SPECTROMETRY, IDENTIFICATION IN THE SPLICEOSOMAL C COMPLEX.
  9. "The human 18S U11/U12 snRNP contains a set of novel proteins not found in the U2-dependent spliceosome."
    Will C.L., Schneider C., Hossbach M., Urlaub H., Rauhut R., Elbashir S., Tuschl T., Luehrmann R.
    RNA 10:929-941(2003) [PubMed] [Europe PMC] [Abstract]
    Cited for: IDENTIFICATION IN A COMPLEX WITH THE U11/U12 SPLICEOSOME, IDENTIFICATION BY MASS SPECTROMETRY.
  10. "An assembly chaperone collaborates with the SMN complex to generate spliceosomal SnRNPs."
    Chari A., Golas M.M., Klingenhager M., Neuenkirchen N., Sander B., Englbrecht C., Sickmann A., Stark H., Fischer U.
    Cell 135:497-509(2007) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION IN SNRNP BIOGENESIS, IDENTIFICATION IN 6S PICLN-SM COMPLEX, IDENTIFICATION IN SMN-SM COMPLEX, SUBCELLULAR LOCATION.
  11. Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
  12. "An enzyme assisted RP-RPLC approach for in-depth analysis of human liver phosphoproteome."
    Bian Y., Song C., Cheng K., Dong M., Wang F., Huang J., Sun D., Wang L., Ye M., Zou H.
    J. Proteomics 96:253-262(2013) [PubMed] [Europe PMC] [Abstract]
    Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
    Tissue: Liver.
  13. "Crystal structure of human spliceosomal U1 snRNP at 5.5 A resolution."
    Pomeranz Krummel D.A., Oubridge C., Leung A.K., Li J., Nagai K.
    Nature 458:475-480(2008) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (5.49 ANGSTROMS) IN SPLICEOSOMAL U1 SNRNP.
  14. "Structure of the spliceosomal U4 snRNP core domain and its implication for snRNP biogenesis."
    Leung A.K., Nagai K., Li J.
    Nature 473:536-539(2010) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (3.60 ANGSTROMS) IN SPLICEOSOMAL CORE U4 SNRNP.
  15. "Structural basis of assembly chaperone-mediated snRNP formation."
    Grimm C., Chari A., Pelz J.P., Kuper J., Kisker C., Diederichs K., Stark H., Schindelin H., Fischer U.
    Mol. Cell 49:692-703(2012) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (1.90 ANGSTROMS) IN 6S PICLN-SM COMPLEX, IDENTIFICATION IN 6S PICLN-SM COMPLEX, FUNCTION IN CORE U1 SNRNP BIOGENESIS.

Entry informationi

Entry nameiRUXF_HUMAN
AccessioniPrimary (citable) accession number: P62306
Secondary accession number(s): A2VCR2
, B2R498, Q15356, Q6IBQ1, Q6P4I0
Entry historyi
Integrated into UniProtKB/Swiss-Prot: July 4, 2004
Last sequence update: July 4, 2004
Last modified: March 31, 2015
This is version 110 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 12
    Human chromosome 12: 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

External Data

Dasty 3

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 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.