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Protein

Delta-type opioid receptor

Gene

OPRD1

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

Functioni

G-protein coupled receptor that functions as receptor for endogenous enkephalins and for a subset of other opioids. Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of down-stream effectors, such as adenylate cyclase. Signaling leads to the inhibition of adenylate cyclase activity. Inhibits neurotransmitter release by reducing calcium ion currents and increasing potassium ion conductance. Plays a role in the perception of pain and in opiate-mediated analgesia. Plays a role in developing analgesic tolerance to morphine.3 Publications

GO - Molecular functioni

  1. enkephalin receptor activity Source: UniProtKB
  2. neuropeptide binding Source: GO_Central
  3. opioid receptor activity Source: UniProtKB

GO - Biological processi

  1. adenylate cyclase-inhibiting G-protein coupled receptor signaling pathway Source: Ensembl
  2. adult locomotory behavior Source: Ensembl
  3. cellular response to growth factor stimulus Source: Ensembl
  4. cellular response to hypoxia Source: ParkinsonsUK-UCL
  5. cellular response to toxic substance Source: ParkinsonsUK-UCL
  6. G-protein coupled receptor signaling pathway Source: UniProtKB
  7. G-protein coupled receptor signaling pathway, coupled to cyclic nucleotide second messenger Source: ProtInc
  8. immune response Source: ProtInc
  9. negative regulation of gene expression Source: ParkinsonsUK-UCL
  10. negative regulation of protein oligomerization Source: ParkinsonsUK-UCL
  11. neuropeptide signaling pathway Source: GO_Central
  12. opioid receptor signaling pathway Source: UniProtKB
  13. phospholipase C-activating G-protein coupled receptor signaling pathway Source: UniProtKB
  14. positive regulation of CREB transcription factor activity Source: ParkinsonsUK-UCL
  15. positive regulation of peptidyl-serine phosphorylation Source: ParkinsonsUK-UCL
  16. protein import into nucleus, translocation Source: UniProtKB
  17. regulation of calcium ion transport Source: Ensembl
  18. regulation of mitochondrial membrane potential Source: ParkinsonsUK-UCL
  19. regulation of sensory perception of pain Source: Ensembl
  20. sensory perception of pain Source: GO_Central
  21. synaptic transmission Source: GO_Central
Complete GO annotation...

Keywords - Molecular functioni

G-protein coupled receptor, Receptor, Transducer

Enzyme and pathway databases

ReactomeiREACT_14819. Peptide ligand-binding receptors.
REACT_19231. G alpha (i) signalling events.
SignaLinkiP41143.

Names & Taxonomyi

Protein namesi
Recommended name:
Delta-type opioid receptor
Short name:
D-OR-1
Short name:
DOR-1
Gene namesi
Name:OPRD1
Synonyms:OPRD
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
ProteomesiUP000005640: Chromosome 1

Organism-specific databases

HGNCiHGNC:8153. OPRD1.

Subcellular locationi

Cell membrane 3 Publications; Multi-pass membrane protein 3 Publications

Topology

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Topological domaini1 – 4747ExtracellularBy similarityAdd
BLAST
Transmembranei48 – 7528Helical; Name=1By similarityAdd
BLAST
Topological domaini76 – 8510CytoplasmicBy similarity
Transmembranei86 – 11025Helical; Name=2By similarityAdd
BLAST
Topological domaini111 – 12212ExtracellularBy similarityAdd
BLAST
Transmembranei123 – 14422Helical; Name=3By similarityAdd
BLAST
Topological domaini145 – 16319CytoplasmicBy similarityAdd
BLAST
Transmembranei164 – 18623Helical; Name=4By similarityAdd
BLAST
Topological domaini187 – 20620ExtracellularBy similarityAdd
BLAST
Transmembranei207 – 23832Helical; Name=5By similarityAdd
BLAST
Topological domaini239 – 26123CytoplasmicBy similarityAdd
BLAST
Transmembranei262 – 28423Helical; Name=6By similarityAdd
BLAST
Topological domaini285 – 29915ExtracellularBy similarityAdd
BLAST
Transmembranei300 – 32122Helical; Name=7By similarityAdd
BLAST
Topological domaini322 – 37251CytoplasmicBy similarityAdd
BLAST

GO - Cellular componenti

  1. axon terminus Source: Ensembl
  2. cytoplasm Source: Ensembl
  3. dendrite membrane Source: Ensembl
  4. integral component of plasma membrane Source: ProtInc
  5. intrinsic component of plasma membrane Source: UniProtKB
  6. membrane raft Source: Ensembl
  7. neuron projection Source: GO_Central
  8. plasma membrane Source: Reactome
  9. postsynaptic membrane Source: Ensembl
  10. vesicle Source: Ensembl
Complete GO annotation...

Keywords - Cellular componenti

Cell membrane, Membrane

Pathology & Biotechi

Organism-specific databases

PharmGKBiPA31942.

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Chaini1 – 372372Delta-type opioid receptorPRO_0000069962Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Glycosylationi18 – 181N-linked (GlcNAc...)Sequence Analysis
Glycosylationi33 – 331N-linked (GlcNAc...)Sequence Analysis
Disulfide bondi121 ↔ 198PROSITE-ProRule annotation
Lipidationi333 – 3331S-palmitoyl cysteineSequence Analysis

Post-translational modificationi

N-glycosylated.1 Publication

Keywords - PTMi

Disulfide bond, Glycoprotein, Lipoprotein, Palmitate

Proteomic databases

PaxDbiP41143.
PRIDEiP41143.

PTM databases

PhosphoSiteiP41143.

Expressioni

Tissue specificityi

Detected in oocytes (at protein level). Detected in brain cortex, hypothalamus, hippocampus and olfactory bulb. Detected in oocytes.2 Publications

Gene expression databases

BgeeiP41143.
CleanExiHS_OPRD1.
ExpressionAtlasiP41143. baseline.
GenevestigatoriP41143.

Organism-specific databases

HPAiHPA013744.

Interactioni

Subunit structurei

May form homooligomers. Interacts with GPRASP1.3 Publications

Binary interactionsi

WithEntry#Exp.IntActNotes
ATP2A2P116072EBI-2624456,EBI-8004986From a different organism.
ATP2A2P166153EBI-2624456,EBI-358933
CANXP278242EBI-2624456,EBI-355947
GPRASP1Q5JY772EBI-2624456,EBI-2514717

Protein-protein interaction databases

BioGridi111030. 11 interactions.
IntActiP41143. 4 interactions.
MINTiMINT-7889289.
STRINGi9606.ENSP00000234961.

Structurei

Secondary structure

1
372
Legend: HelixTurnBeta strand
Show more details
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Helixi40 – 7637Combined sources
Helixi78 – 803Combined sources
Helixi83 – 10018Combined sources
Helixi102 – 11110Combined sources
Helixi118 – 15134Combined sources
Turni153 – 1553Combined sources
Helixi156 – 1594Combined sources
Helixi162 – 18625Combined sources
Beta strandi187 – 1926Combined sources
Beta strandi195 – 2006Combined sources
Beta strandi203 – 2053Combined sources
Helixi206 – 22015Combined sources
Helixi223 – 24220Combined sources
Beta strandi246 – 2494Combined sources
Helixi250 – 28637Combined sources
Helixi294 – 32128Combined sources
Helixi323 – 33412Combined sources

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
1OZCmodel-A1-372[»]
2IQMmodel-A45-336[»]
4N6HX-ray1.80A36-338[»]
ProteinModelPortaliP41143.
SMRiP41143. Positions 36-338.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Sequence similaritiesi

Belongs to the G-protein coupled receptor 1 family.PROSITE-ProRule annotation

Keywords - Domaini

Transmembrane, Transmembrane helix

Phylogenomic databases

eggNOGiNOG241795.
GeneTreeiENSGT00760000118797.
HOGENOMiHOG000230486.
HOVERGENiHBG106919.
InParanoidiP41143.
KOiK04213.
OMAiLCRKPCG.
OrthoDBiEOG7BKCVQ.
PhylomeDBiP41143.
TreeFamiTF315737.

Family and domain databases

InterProiIPR000321. Delta_opi_rcpt.
IPR000276. GPCR_Rhodpsn.
IPR017452. GPCR_Rhodpsn_7TM.
IPR001418. Opioid_rcpt.
[Graphical view]
PfamiPF00001. 7tm_1. 1 hit.
[Graphical view]
PRINTSiPR00525. DELTAOPIOIDR.
PR00237. GPCRRHODOPSN.
PR00384. OPIOIDR.
PROSITEiPS00237. G_PROTEIN_RECEP_F1_1. 1 hit.
PS50262. G_PROTEIN_RECEP_F1_2. 1 hit.
[Graphical view]

Sequencei

Sequence statusi: Complete.

P41143-1 [UniParc]FASTAAdd to Basket

« Hide

        10         20         30         40         50
MEPAPSAGAE LQPPLFANAS DAYPSACPSA GANASGPPGA RSASSLALAI
60 70 80 90 100
AITALYSAVC AVGLLGNVLV MFGIVRYTKM KTATNIYIFN LALADALATS
110 120 130 140 150
TLPFQSAKYL METWPFGELL CKAVLSIDYY NMFTSIFTLT MMSVDRYIAV
160 170 180 190 200
CHPVKALDFR TPAKAKLINI CIWVLASGVG VPIMVMAVTR PRDGAVVCML
210 220 230 240 250
QFPSPSWYWD TVTKICVFLF AFVVPILIIT VCYGLMLLRL RSVRLLSGSK
260 270 280 290 300
EKDRSLRRIT RMVLVVVGAF VVCWAPIHIF VIVWTLVDID RRDPLVVAAL
310 320 330 340 350
HLCIALGYAN SSLNPVLYAF LDENFKRCFR QLCRKPCGRP DPSSFSRARE
360 370
ATARERVTAC TPSDGPGGGA AA
Length:372
Mass (Da):40,369
Last modified:November 2, 2010 - v4
Checksum:i9D483FC39BA2BAE4
GO

Natural variant

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Natural varianti27 – 271C → F Improved maturation and increased expression at the cell surface. 4 Publications
Corresponds to variant rs1042114 [ dbSNP | Ensembl ].
VAR_012083

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
U07882 mRNA. Translation: AAA18789.2.
U10504 mRNA. Translation: AAA83426.1.
EU883570 mRNA. Translation: ACG60644.1.
AL009181 Genomic DNA. Translation: CAA15671.1.
CCDSiCCDS329.1.
PIRiI38532.
RefSeqiNP_000902.3. NM_000911.3.
UniGeneiHs.372.

Genome annotation databases

EnsembliENST00000234961; ENSP00000234961; ENSG00000116329.
GeneIDi4985.
KEGGihsa:4985.
UCSCiuc001brf.1. human.

Polymorphism databases

DMDMi311033488.

Keywords - Coding sequence diversityi

Polymorphism

Cross-referencesi

Web resourcesi

Wikipedia

Delta opioid receptor entry

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
U07882 mRNA. Translation: AAA18789.2.
U10504 mRNA. Translation: AAA83426.1.
EU883570 mRNA. Translation: ACG60644.1.
AL009181 Genomic DNA. Translation: CAA15671.1.
CCDSiCCDS329.1.
PIRiI38532.
RefSeqiNP_000902.3. NM_000911.3.
UniGeneiHs.372.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
1OZCmodel-A1-372[»]
2IQMmodel-A45-336[»]
4N6HX-ray1.80A36-338[»]
ProteinModelPortaliP41143.
SMRiP41143. Positions 36-338.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi111030. 11 interactions.
IntActiP41143. 4 interactions.
MINTiMINT-7889289.
STRINGi9606.ENSP00000234961.

Chemistry

BindingDBiP41143.
ChEMBLiCHEMBL2095149.
DrugBankiDB06274. Alvimopan.
DB00321. Amitriptyline.
DB00921. Buprenorphine.
DB00611. Butorphanol.
DB00318. Codeine.
DB00514. Dextromethorphan.
DB00647. Dextropropoxyphene.
DB01081. Diphenoxylate.
DB00813. Fentanyl.
DB01452. Heroin.
DB00956. Hydrocodone.
DB00327. Hydromorphone.
DB01221. Ketamine.
DB06738. Ketobemidone.
DB00854. Levorphanol.
DB00836. Loperamide.
DB00333. Methadone.
DB00295. Morphine.
DB00844. Nalbuphine.
DB01183. Naloxone.
DB00704. Naltrexone.
DB00497. Oxycodone.
DB01192. Oxymorphone.
DB00899. Remifentanil.
DB00708. Sufentanil.
DB06204. Tapentadol.
DB00193. Tramadol.
GuidetoPHARMACOLOGYi317.

Protein family/group databases

GPCRDBiSearch...

PTM databases

PhosphoSiteiP41143.

Polymorphism databases

DMDMi311033488.

Proteomic databases

PaxDbiP41143.
PRIDEiP41143.

Protocols and materials databases

DNASUi4985.
Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000234961; ENSP00000234961; ENSG00000116329.
GeneIDi4985.
KEGGihsa:4985.
UCSCiuc001brf.1. human.

Organism-specific databases

CTDi4985.
GeneCardsiGC01P029144.
HGNCiHGNC:8153. OPRD1.
HPAiHPA013744.
MIMi165195. gene.
neXtProtiNX_P41143.
PharmGKBiPA31942.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiNOG241795.
GeneTreeiENSGT00760000118797.
HOGENOMiHOG000230486.
HOVERGENiHBG106919.
InParanoidiP41143.
KOiK04213.
OMAiLCRKPCG.
OrthoDBiEOG7BKCVQ.
PhylomeDBiP41143.
TreeFamiTF315737.

Enzyme and pathway databases

ReactomeiREACT_14819. Peptide ligand-binding receptors.
REACT_19231. G alpha (i) signalling events.
SignaLinkiP41143.

Miscellaneous databases

GeneWikii%CE%94-opioid_receptor.
GenomeRNAii4985.
NextBioi19190.
PROiP41143.
SOURCEiSearch...

Gene expression databases

BgeeiP41143.
CleanExiHS_OPRD1.
ExpressionAtlasiP41143. baseline.
GenevestigatoriP41143.

Family and domain databases

InterProiIPR000321. Delta_opi_rcpt.
IPR000276. GPCR_Rhodpsn.
IPR017452. GPCR_Rhodpsn_7TM.
IPR001418. Opioid_rcpt.
[Graphical view]
PfamiPF00001. 7tm_1. 1 hit.
[Graphical view]
PRINTSiPR00525. DELTAOPIOIDR.
PR00237. GPCRRHODOPSN.
PR00384. OPIOIDR.
PROSITEiPS00237. G_PROTEIN_RECEP_F1_1. 1 hit.
PS50262. G_PROTEIN_RECEP_F1_2. 1 hit.
[Graphical view]
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. Cited for: NUCLEOTIDE SEQUENCE [MRNA], FUNCTION, SUBCELLULAR LOCATION, VARIANT PHE-27.
    Tissue: Brain cortex and Corpus striatum.
  2. Knapp R.J.
    Submitted (JAN-2003) to the EMBL/GenBank/DDBJ databases
    Cited for: SEQUENCE REVISION TO 40-41; 348 AND 370.
  3. "The human delta-opioid receptor: genomic organization, cDNA cloning, functional expression, and distribution in human brain."
    Simonin F., Befort K., Gaveriaux-Ruff C., Matthes H., Nappey V., Lannes B., Micheletti G., Kieffer B.
    Mol. Pharmacol. 46:1015-1021(1994) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA], FUNCTION, SUBCELLULAR LOCATION, TISSUE SPECIFICITY.
  4. "Isolation of cDNA coding for human opioid receptor, delta 1 (OPRD1)."
    Kaighin V.A., Martin A.L., Aronstam R.S.
    Submitted (JUL-2008) to the EMBL/GenBank/DDBJ databases
    Cited for: NUCLEOTIDE SEQUENCE [MRNA], VARIANT PHE-27.
    Tissue: Kidney.
  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. "Modulation of postendocytic sorting of G protein-coupled receptors."
    Whistler J.L., Enquist J., Marley A., Fong J., Gladher F., Tsuruda P., Murray S.R., Von Zastrow M.
    Science 297:615-620(2002) [PubMed] [Europe PMC] [Abstract]
    Cited for: INTERACTION WITH GPRASP1.
  7. "Identification of a novel family of G protein-coupled receptor associated sorting proteins."
    Simonin F., Karcher P., Boeuf J.J.-M., Matifas A., Kieffer B.L.
    J. Neurochem. 89:766-775(2004) [PubMed] [Europe PMC] [Abstract]
    Cited for: INTERACTION WITH GPRASP1.
  8. "Cys-27 variant of human delta-opioid receptor modulates maturation and cell surface delivery of Phe-27 variant via heteromerization."
    Leskela T.T., Lackman J.J., Vierimaa M.M., Kobayashi H., Bouvier M., Petaja-Repo U.E.
    J. Biol. Chem. 287:5008-5020(2012) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, SUBCELLULAR LOCATION, GLYCOSYLATION, SUBUNIT, CHARACTERIZATION OF VARIANT PHE-27.
  9. "Expression and localization of opioid receptors during the maturation of human oocytes."
    Agirregoitia E., Peralta L., Mendoza R., Exposito A., Ereno E.D., Matorras R., Agirregoitia N.
    Reprod. BioMed. Online 24:550-557(2012) [PubMed] [Europe PMC] [Abstract]
    Cited for: TISSUE SPECIFICITY.
  10. "Variant detection at the delta opioid receptor (OPRD1) locus and population genetics of a novel variant affecting protein sequence."
    Gelernter J., Kranzler H.R.
    Hum. Genet. 107:86-88(2000) [PubMed] [Europe PMC] [Abstract]
    Cited for: VARIANT PHE-27.
  11. "Opioid receptor random mutagenesis reveals a mechanism for G protein-coupled receptor activation."
    Decaillot F.M., Befort K., Filliol D., Yue S., Walker P., Kieffer B.L.
    Nat. Struct. Biol. 10:629-636(2003) [PubMed] [Europe PMC] [Abstract]
    Cited for: 3D-STRUCTURE MODELING.

Entry informationi

Entry nameiOPRD_HUMAN
AccessioniPrimary (citable) accession number: P41143
Secondary accession number(s): B5B0B8
Entry historyi
Integrated into UniProtKB/Swiss-Prot: February 1, 1995
Last sequence update: November 2, 2010
Last modified: February 4, 2015
This is version 139 of the entry and version 4 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. 7-transmembrane G-linked receptors
    List of 7-transmembrane G-linked receptor entries
  2. Human chromosome 1
    Human chromosome 1: entries, gene names and cross-references to MIM
  3. Human entries with polymorphisms or disease mutations
    List of human entries with polymorphisms or disease mutations
  4. Human polymorphisms and disease mutations
    Index of human polymorphisms and disease mutations
  5. MIM cross-references
    Online Mendelian Inheritance in Man (MIM) cross-references in UniProtKB/Swiss-Prot
  6. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  7. 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.