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Protein

Sodium/potassium-transporting ATPase subunit beta-1

Gene

ATP1B1

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

Functioni

This is the non-catalytic component of the active enzyme, which catalyzes the hydrolysis of ATP coupled with the exchange of Na+ and K+ ions across the plasma membrane. The beta subunit regulates, through assembly of alpha/beta heterodimers, the number of sodium pumps transported to the plasma membrane.1 Publication
Involved in cell adhesion and establishing epithelial cell polarity.1 Publication

GO - Molecular functioni

  • ATPase activator activity Source: BHF-UCL
  • ATPase binding Source: BHF-UCL
  • MHC class II protein complex binding Source: UniProtKB
  • sodium:potassium-exchanging ATPase activity Source: Ensembl

GO - Biological processi

  • activation of mitophagy in response to mitochondrial depolarization Source: ParkinsonsUK-UCL
  • blood coagulation Source: Reactome
  • cardiac muscle contraction Source: BHF-UCL
  • cell adhesion Source: UniProtKB-KW
  • cell communication by electrical coupling involved in cardiac conduction Source: BHF-UCL
  • cellular calcium ion homeostasis Source: BHF-UCL
  • cellular potassium ion homeostasis Source: BHF-UCL
  • cellular sodium ion homeostasis Source: BHF-UCL
  • ion transmembrane transport Source: Reactome
  • leukocyte migration Source: Reactome
  • membrane repolarization Source: BHF-UCL
  • membrane repolarization during cardiac muscle cell action potential Source: BHF-UCL
  • positive regulation of ATPase activity Source: BHF-UCL
  • positive regulation of calcium:sodium antiporter activity Source: BHF-UCL
  • positive regulation of defense response to virus by host Source: ParkinsonsUK-UCL
  • positive regulation of potassium ion import Source: BHF-UCL
  • positive regulation of potassium ion transmembrane transporter activity Source: BHF-UCL
  • positive regulation of sodium ion export from cell Source: BHF-UCL
  • potassium ion import Source: BHF-UCL
  • potassium ion import across plasma membrane Source: BHF-UCL
  • protein localization to plasma membrane Source: BHF-UCL
  • protein stabilization Source: BHF-UCL
  • protein transport into plasma membrane raft Source: BHF-UCL
  • regulation of cardiac muscle contraction by calcium ion signaling Source: BHF-UCL
  • regulation of gene expression Source: BHF-UCL
  • relaxation of cardiac muscle Source: BHF-UCL
  • response to hypoxia Source: Ensembl
  • sodium ion export from cell Source: BHF-UCL
  • transmembrane transport Source: Reactome
Complete GO annotation...

Keywords - Biological processi

Cell adhesion, Ion transport, Potassium transport, Sodium transport, Sodium/potassium transport, Transport

Keywords - Ligandi

Potassium, Sodium

Enzyme and pathway databases

ReactomeiREACT_12560. Basigin interactions.
REACT_25149. Ion transport by P-type ATPases.

Protein family/group databases

TCDBi3.A.3.1.1. the p-type atpase (p-atpase) superfamily.

Names & Taxonomyi

Protein namesi
Recommended name:
Sodium/potassium-transporting ATPase subunit beta-1
Alternative name(s):
Sodium/potassium-dependent ATPase subunit beta-1
Gene namesi
Name:ATP1B1
Synonyms:ATP1B
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
ProteomesiUP000005640 Componenti: Chromosome 1

Organism-specific databases

HGNCiHGNC:804. ATP1B1.

Subcellular locationi

Topology

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Topological domaini1 – 3434CytoplasmicSequence AnalysisAdd
BLAST
Transmembranei35 – 6228Helical; Signal-anchor for type II membrane proteinSequence AnalysisAdd
BLAST
Topological domaini63 – 303241ExtracellularSequence AnalysisAdd
BLAST

GO - Cellular componenti

  • apical plasma membrane Source: Ensembl
  • basolateral plasma membrane Source: Ensembl
  • caveola Source: Ensembl
  • extracellular exosome Source: UniProtKB
  • intercalated disc Source: BHF-UCL
  • plasma membrane Source: BHF-UCL
  • sarcolemma Source: BHF-UCL
  • sodium:potassium-exchanging ATPase complex Source: BHF-UCL
  • vesicle Source: UniProtKB
Complete GO annotation...

Keywords - Cellular componenti

Cell membrane, Membrane

Pathology & Biotechi

Organism-specific databases

PharmGKBiPA66.

Polymorphism and mutation databases

BioMutaiATP1B1.
DMDMi114392.

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Chaini1 – 303303Sodium/potassium-transporting ATPase subunit beta-1PRO_0000219097Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei101 – 1011PhosphotyrosineBy similarity
Disulfide bondi126 ↔ 149By similarity
Glycosylationi158 – 1581N-linked (GlcNAc...)2 Publications
Disulfide bondi159 ↔ 175By similarity
Glycosylationi193 – 1931N-linked (GlcNAc...)2 Publications
Disulfide bondi213 ↔ 276By similarity
Glycosylationi265 – 2651N-linked (GlcNAc...)3 Publications

Keywords - PTMi

Disulfide bond, Glycoprotein, Phosphoprotein

Proteomic databases

MaxQBiP05026.
PaxDbiP05026.
PRIDEiP05026.

PTM databases

PhosphoSiteiP05026.

Expressioni

Tissue specificityi

Found in most tissues.

Gene expression databases

BgeeiP05026.
CleanExiHS_ATP1B1.
ExpressionAtlasiP05026. baseline and differential.
GenevestigatoriP05026.

Organism-specific databases

HPAiHPA012911.

Interactioni

Subunit structurei

Composed of three subunits: alpha (catalytic), beta and gamma. Interacts with NKAIN1, NKAIN2 and NKAIN4 (By similarity). Interacts with MLC1. Part of a complex containing MLC1, TRPV4, AQP4 and HEPACAM.By similarity1 Publication

Protein-protein interaction databases

BioGridi106971. 26 interactions.
IntActiP05026. 11 interactions.
MINTiMINT-5000887.
STRINGi9606.ENSP00000356789.

Structurei

3D structure databases

ProteinModelPortaliP05026.
SMRiP05026. Positions 1-303.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Region

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Regioni191 – 303113immunoglobulin-likeAdd
BLAST

Domaini

The C-terminal lobe folds into an immunoglobulin-like domain and mediates cell adhesion properties.By similarity

Sequence similaritiesi

Keywords - Domaini

Signal-anchor, Transmembrane, Transmembrane helix

Phylogenomic databases

eggNOGiNOG313139.
GeneTreeiENSGT00550000074530.
HOGENOMiHOG000039248.
HOVERGENiHBG050603.
InParanoidiP05026.
KOiK01540.
OMAiNVEYFGL.
OrthoDBiEOG7M6D85.
PhylomeDBiP05026.
TreeFamiTF314618.

Family and domain databases

InterProiIPR000402. Na/K_ATPase_sub_beta.
IPR015565. Na/K_ATPase_sub_beta_chordates.
[Graphical view]
PANTHERiPTHR11523. PTHR11523. 1 hit.
PTHR11523:SF10. PTHR11523:SF10. 1 hit.
PfamiPF00287. Na_K-ATPase. 1 hit.
[Graphical view]
TIGRFAMsiTIGR01107. Na_K_ATPase_bet. 1 hit.
PROSITEiPS00390. ATPASE_NA_K_BETA_1. 1 hit.
PS00391. ATPASE_NA_K_BETA_2. 1 hit.
[Graphical view]

Sequences (2)i

Sequence statusi: Complete.

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

Isoform 1 (identifier: P05026-1) [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
MARGKAKEEG SWKKFIWNSE KKEFLGRTGG SWFKILLFYV IFYGCLAGIF
60 70 80 90 100
IGTIQVMLLT ISEFKPTYQD RVAPPGLTQI PQIQKTEISF RPNDPKSYEA
110 120 130 140 150
YVLNIVRFLE KYKDSAQRDD MIFEDCGDVP SEPKERGDFN HERGERKVCR
160 170 180 190 200
FKLEWLGNCS GLNDETYGYK EGKPCIIIKL NRVLGFKPKP PKNESLETYP
210 220 230 240 250
VMKYNPNVLP VQCTGKRDED KDKVGNVEYF GLGNSPGFPL QYYPYYGKLL
260 270 280 290 300
QPKYLQPLLA VQFTNLTMDT EIRIECKAYG ENIGYSEKDR FQGRFDVKIE

VKS
Length:303
Mass (Da):35,061
Last modified:August 13, 1987 - v1
Checksum:i107D3C04394F2D11
GO
Isoform 2 (identifier: P05026-2) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     300-303: EVKS → KF

Show »
Length:301
Mass (Da):34,893
Checksum:i670C194F2D114F67
GO

Alternative sequence

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Alternative sequencei300 – 3034EVKS → KF in isoform 2. 1 PublicationVSP_000349

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
X03747 mRNA. Translation: CAA27385.1.
M25160, M25161 Genomic DNA. Translation: AAA36352.1.
U16799 mRNA. Translation: AAC50132.1.
BT009787 mRNA. Translation: AAP88789.1.
AL031726 Genomic DNA. Translation: CAI18888.1.
BC000006 mRNA. Translation: AAH00006.1.
X17161 Genomic DNA. Translation: CAA35040.1.
CCDSiCCDS1276.1. [P05026-1]
PIRiA23764. PWHUNB.
RefSeqiNP_001668.1. NM_001677.3. [P05026-1]
UniGeneiHs.291196.

Genome annotation databases

EnsembliENST00000367815; ENSP00000356789; ENSG00000143153. [P05026-1]
ENST00000367816; ENSP00000356790; ENSG00000143153. [P05026-1]
GeneIDi481.
KEGGihsa:481.
UCSCiuc001gfr.1. human. [P05026-1]

Keywords - Coding sequence diversityi

Alternative splicing

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
X03747 mRNA. Translation: CAA27385.1.
M25160, M25161 Genomic DNA. Translation: AAA36352.1.
U16799 mRNA. Translation: AAC50132.1.
BT009787 mRNA. Translation: AAP88789.1.
AL031726 Genomic DNA. Translation: CAI18888.1.
BC000006 mRNA. Translation: AAH00006.1.
X17161 Genomic DNA. Translation: CAA35040.1.
CCDSiCCDS1276.1. [P05026-1]
PIRiA23764. PWHUNB.
RefSeqiNP_001668.1. NM_001677.3. [P05026-1]
UniGeneiHs.291196.

3D structure databases

ProteinModelPortaliP05026.
SMRiP05026. Positions 1-303.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi106971. 26 interactions.
IntActiP05026. 11 interactions.
MINTiMINT-5000887.
STRINGi9606.ENSP00000356789.

Chemistry

ChEMBLiCHEMBL2095186.

Protein family/group databases

TCDBi3.A.3.1.1. the p-type atpase (p-atpase) superfamily.

PTM databases

PhosphoSiteiP05026.

Polymorphism and mutation databases

BioMutaiATP1B1.
DMDMi114392.

Proteomic databases

MaxQBiP05026.
PaxDbiP05026.
PRIDEiP05026.

Protocols and materials databases

DNASUi481.
Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000367815; ENSP00000356789; ENSG00000143153. [P05026-1]
ENST00000367816; ENSP00000356790; ENSG00000143153. [P05026-1]
GeneIDi481.
KEGGihsa:481.
UCSCiuc001gfr.1. human. [P05026-1]

Organism-specific databases

CTDi481.
GeneCardsiGC01P169074.
H-InvDBHIX0001311.
HGNCiHGNC:804. ATP1B1.
HPAiHPA012911.
MIMi182330. gene.
neXtProtiNX_P05026.
PharmGKBiPA66.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiNOG313139.
GeneTreeiENSGT00550000074530.
HOGENOMiHOG000039248.
HOVERGENiHBG050603.
InParanoidiP05026.
KOiK01540.
OMAiNVEYFGL.
OrthoDBiEOG7M6D85.
PhylomeDBiP05026.
TreeFamiTF314618.

Enzyme and pathway databases

ReactomeiREACT_12560. Basigin interactions.
REACT_25149. Ion transport by P-type ATPases.

Miscellaneous databases

ChiTaRSiATP1B1. human.
GeneWikiiATP1B1.
GenomeRNAii481.
NextBioi1995.
PROiP05026.
SOURCEiSearch...

Gene expression databases

BgeeiP05026.
CleanExiHS_ATP1B1.
ExpressionAtlasiP05026. baseline and differential.
GenevestigatoriP05026.

Family and domain databases

InterProiIPR000402. Na/K_ATPase_sub_beta.
IPR015565. Na/K_ATPase_sub_beta_chordates.
[Graphical view]
PANTHERiPTHR11523. PTHR11523. 1 hit.
PTHR11523:SF10. PTHR11523:SF10. 1 hit.
PfamiPF00287. Na_K-ATPase. 1 hit.
[Graphical view]
TIGRFAMsiTIGR01107. Na_K_ATPase_bet. 1 hit.
PROSITEiPS00390. ATPASE_NA_K_BETA_1. 1 hit.
PS00391. ATPASE_NA_K_BETA_2. 1 hit.
[Graphical view]
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "Molecular cloning and sequence analysis of human Na,K-ATPase beta-subunit."
    Kawakami K., Nojima H., Ohta T., Nagano K.
    Nucleic Acids Res. 14:2833-2844(1986) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 1).
  2. "Characterization of two genes for the human Na,K-ATPase beta subunit."
    Lane L.K., Shull M.M., Whitmer K.R., Lingrel J.B.
    Genomics 5:445-453(1989) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA].
  3. "Characterization and quantification of full-length and truncated Na,K-ATPase alpha 1 and beta 1 RNA transcripts expressed in human retinal pigment epithelium."
    Ruiz A., Bhat S.P., Bok D.
    Gene 155:179-184(1995) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 2).
    Tissue: Retinal pigment epithelium.
  4. "Cloning of human full-length CDSs in BD Creator(TM) system donor vector."
    Kalnine N., Chen X., Rolfs A., Halleck A., Hines L., Eisenstein S., Koundinya M., Raphael J., Moreira D., Kelley T., LaBaer J., Lin Y., Phelan M., Farmer A.
    Submitted (AUG-2003) to the EMBL/GenBank/DDBJ databases
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA] (ISOFORM 1).
  5. "The DNA sequence and biological annotation of human chromosome 1."
    Gregory S.G., Barlow K.F., McLay K.E., Kaul R., Swarbreck D., Dunham A., Scott C.E., Howe K.L., Woodfine K., Spencer C.C.A., Jones M.C., Gillson C., Searle S., Zhou Y., Kokocinski F., McDonald L., Evans R., Phillips K.
    , Atkinson A., Cooper R., Jones C., Hall R.E., Andrews T.D., Lloyd C., Ainscough R., Almeida J.P., Ambrose K.D., Anderson F., Andrew R.W., Ashwell R.I.S., Aubin K., Babbage A.K., Bagguley C.L., Bailey J., Beasley H., Bethel G., Bird C.P., Bray-Allen S., Brown J.Y., Brown A.J., Buckley D., Burton J., Bye J., Carder C., Chapman J.C., Clark S.Y., Clarke G., Clee C., Cobley V., Collier R.E., Corby N., Coville G.J., Davies J., Deadman R., Dunn M., Earthrowl M., Ellington A.G., Errington H., Frankish A., Frankland J., French L., Garner P., Garnett J., Gay L., Ghori M.R.J., Gibson R., Gilby L.M., Gillett W., Glithero R.J., Grafham D.V., Griffiths C., Griffiths-Jones S., Grocock R., Hammond S., Harrison E.S.I., Hart E., Haugen E., Heath P.D., Holmes S., Holt K., Howden P.J., Hunt A.R., Hunt S.E., Hunter G., Isherwood J., James R., Johnson C., Johnson D., Joy A., Kay M., Kershaw J.K., Kibukawa M., Kimberley A.M., King A., Knights A.J., Lad H., Laird G., Lawlor S., Leongamornlert D.A., Lloyd D.M., Loveland J., Lovell J., Lush M.J., Lyne R., Martin S., Mashreghi-Mohammadi M., Matthews L., Matthews N.S.W., McLaren S., Milne S., Mistry S., Moore M.J.F., Nickerson T., O'Dell C.N., Oliver K., Palmeiri A., Palmer S.A., Parker A., Patel D., Pearce A.V., Peck A.I., Pelan S., Phelps K., Phillimore B.J., Plumb R., Rajan J., Raymond C., Rouse G., Saenphimmachak C., Sehra H.K., Sheridan E., Shownkeen R., Sims S., Skuce C.D., Smith M., Steward C., Subramanian S., Sycamore N., Tracey A., Tromans A., Van Helmond Z., Wall M., Wallis J.M., White S., Whitehead S.L., Wilkinson J.E., Willey D.L., Williams H., Wilming L., Wray P.W., Wu Z., Coulson A., Vaudin M., Sulston J.E., Durbin R.M., Hubbard T., Wooster R., Dunham I., Carter N.P., McVean G., Ross M.T., Harrow J., Olson M.V., Beck S., Rogers J., Bentley D.R.
    Nature 441:315-321(2006) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
  6. "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(2004) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA] (ISOFORM 1).
    Tissue: Kidney.
  7. "Human Na(+), K(+)-ATPase genes. Beta subunit gene family contains at least one gene and one pseudogene."
    Ushkaryov Y.A., Monastyrskaya G.S., Broude N.E., Nikiforova N.N., Bessarab B.A., Orlova M.Y., Petrukhin K.E., Modyanov N.N., Sverdlov E.D.
    FEBS Lett. 257:439-442(1989) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA] OF 34-72.
    Tissue: Sperm.
  8. "Identification and quantification of N-linked glycoproteins using hydrazide chemistry, stable isotope labeling and mass spectrometry."
    Zhang H., Li X.-J., Martin D.B., Aebersold R.
    Nat. Biotechnol. 21:660-666(2003) [PubMed] [Europe PMC] [Abstract]
    Cited for: GLYCOSYLATION AT ASN-158; ASN-193 AND ASN-265.
  9. "A C-terminal lobe of the beta subunit of Na,K-ATPase and H,K-ATPase resembles cell adhesion molecules."
    Bab-Dinitz E., Albeck S., Peleg Y., Brumfeld V., Gottschalk K.E., Karlish S.J.
    Biochemistry 48:8684-8691(2009) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION IN ADHESION, DOMAIN IMMUNOGLOBULIN-LIKE.
  10. "Glycoproteomics analysis of human liver tissue by combination of multiple enzyme digestion and hydrazide chemistry."
    Chen R., Jiang X., Sun D., Han G., Wang F., Ye M., Wang L., Zou H.
    J. Proteome Res. 8:651-661(2009) [PubMed] [Europe PMC] [Abstract]
    Cited for: GLYCOSYLATION [LARGE SCALE ANALYSIS] AT ASN-158; ASN-193 AND ASN-265.
    Tissue: Liver.
  11. "Mass-spectrometric identification and relative quantification of N-linked cell surface glycoproteins."
    Wollscheid B., Bausch-Fluck D., Henderson C., O'Brien R., Bibel M., Schiess R., Aebersold R., Watts J.D.
    Nat. Biotechnol. 27:378-386(2009) [PubMed] [Europe PMC] [Abstract]
    Cited for: GLYCOSYLATION [LARGE SCALE ANALYSIS] AT ASN-265.
    Tissue: Leukemic T-cell.
  12. Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
  13. "Megalencephalic leukoencephalopathy with subcortical cysts protein 1 functionally cooperates with the TRPV4 cation channel to activate the response of astrocytes to osmotic stress: dysregulation by pathological mutations."
    Lanciotti A., Brignone M.S., Molinari P., Visentin S., De Nuccio C., Macchia G., Aiello C., Bertini E., Aloisi F., Petrucci T.C., Ambrosini E.
    Hum. Mol. Genet. 21:2166-2180(2012) [PubMed] [Europe PMC] [Abstract]
    Cited for: INTERACTION WITH MLC1.
  14. "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(2014) [PubMed] [Europe PMC] [Abstract]
    Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
    Tissue: Liver.

Entry informationi

Entry nameiAT1B1_HUMAN
AccessioniPrimary (citable) accession number: P05026
Secondary accession number(s): Q5TGZ3
Entry historyi
Integrated into UniProtKB/Swiss-Prot: August 13, 1987
Last sequence update: August 13, 1987
Last modified: May 27, 2015
This is version 162 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

Complete proteome, Reference proteome

Documents

  1. Human chromosome 1
    Human chromosome 1: 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. 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.