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Protein

Polycystic kidney disease 2-like 2 protein

Gene

PKD2L2

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

Functioni

May function as a subunit of a cation channel and play a role in fertilization.

GO - Molecular functioni

GO - Biological processi

Complete GO annotation...

Keywords - Molecular functioni

Ion channel

Keywords - Biological processi

Ion transport, Transport

Names & Taxonomyi

Protein namesi
Recommended name:
Polycystic kidney disease 2-like 2 protein
Alternative name(s):
Polycystin-2L2
Polycystin-L2
Gene namesi
Name:PKD2L2
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
ProteomesiUP000005640 Componenti: Chromosome 5

Organism-specific databases

HGNCiHGNC:9012. PKD2L2.

Subcellular locationi

Topology

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Topological domaini1 – 3131CytoplasmicSequence AnalysisAdd
BLAST
Transmembranei32 – 5221HelicalSequence AnalysisAdd
BLAST
Topological domaini53 – 276224ExtracellularSequence AnalysisAdd
BLAST
Transmembranei277 – 29721HelicalSequence AnalysisAdd
BLAST
Topological domaini298 – 31417CytoplasmicSequence AnalysisAdd
BLAST
Transmembranei315 – 33521HelicalSequence AnalysisAdd
BLAST
Topological domaini336 – 36025ExtracellularSequence AnalysisAdd
BLAST
Transmembranei361 – 38121HelicalSequence AnalysisAdd
BLAST
Topological domaini382 – 40625CytoplasmicSequence AnalysisAdd
BLAST
Transmembranei407 – 42721HelicalSequence AnalysisAdd
BLAST
Topological domaini428 – 46942ExtracellularSequence AnalysisAdd
BLAST
Transmembranei470 – 49021HelicalSequence AnalysisAdd
BLAST
Topological domaini491 – 624134CytoplasmicSequence AnalysisAdd
BLAST

GO - Cellular componenti

  • integral component of membrane Source: UniProtKB
Complete GO annotation...

Keywords - Cellular componenti

Membrane

Pathology & Biotechi

Organism-specific databases

PharmGKBiPA33345.

Polymorphism and mutation databases

BioMutaiPKD2L2.
DMDMi317373272.

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Chaini1 – 624624Polycystic kidney disease 2-like 2 proteinPRO_0000164361Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Glycosylationi115 – 1151N-linked (GlcNAc...)Sequence Analysis
Glycosylationi138 – 1381N-linked (GlcNAc...)Sequence Analysis

Keywords - PTMi

Glycoprotein

Proteomic databases

PaxDbiQ9NZM6.
PRIDEiQ9NZM6.

PTM databases

PhosphoSiteiQ9NZM6.

Expressioni

Tissue specificityi

According to PubMed:10602361, expressed only in testis. According to PubMed:10756092, expressed also in brain and kidney. Isoform 2 is found only in transformed lymphoblasts. Isoform 3 is found in all tissues tested.

Gene expression databases

BgeeiQ9NZM6.
CleanExiHS_PKD2L2.
ExpressionAtlasiQ9NZM6. baseline and differential.
GenevestigatoriQ9NZM6.

Organism-specific databases

HPAiHPA041903.
HPA043634.

Interactioni

Protein-protein interaction databases

BioGridi117970. 4 interactions.
STRINGi9606.ENSP00000290431.

Structurei

3D structure databases

ProteinModelPortaliQ9NZM6.
SMRiQ9NZM6. Positions 408-492.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Coiled coil

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Coiled coili556 – 57621Sequence AnalysisAdd
BLAST

Motif

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Motifi126 – 13813Polycystin motifAdd
BLAST

Sequence similaritiesi

Belongs to the polycystin family.Curated

Keywords - Domaini

Coiled coil, Transmembrane, Transmembrane helix

Phylogenomic databases

eggNOGiNOG325704.
GeneTreeiENSGT00700000104221.
HOGENOMiHOG000230858.
HOVERGENiHBG014945.
InParanoidiQ9NZM6.
KOiK04991.
OMAiAQFRIVL.
OrthoDBiEOG7N8ZTW.
PhylomeDBiQ9NZM6.
TreeFamiTF316484.

Family and domain databases

InterProiIPR013122. PKD1_2_channel.
IPR003915. PKD_2.
[Graphical view]
PfamiPF08016. PKD_channel. 1 hit.
[Graphical view]
PRINTSiPR01433. POLYCYSTIN2.

Sequences (7)i

Sequence statusi: Complete.

This entry describes 7 isoformsi produced by alternative splicing. AlignAdd to basket

Note: Experimental confirmation may be lacking for some isoforms.

Isoform 1 (identifier: Q9NZM6-1) [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
MAEASRWHRG GASKHKLHYR KEVEITTTLQ ELLLYFIFLI NLCILTFGMV
60 70 80 90 100
NPHMYYLNKV MSSLFLDTSV PGEERTNFKS IRSITDFWKF MEGPLLEGLY
110 120 130 140 150
WDSWYNNQQL YNLKNSSRIY YENILLGVPR VRQLKVRNNT CKVYSSFQSL
160 170 180 190 200
MSECYGKYTS ANEDLSNFGL QINTEWRYST SNTNSPWHWG FLGVYRNGGY
210 220 230 240 250
IFTLSKSKSE TKNKFIDLRL NSWITRGTRV IFIDFSLYNA NVNLFCIIRL
260 270 280 290 300
VAEFPATGGI LTSWQFYSVK LLRYVSYYDY FIASCEITFC IFLFVFTTQE
310 320 330 340 350
VKKIKEFKSA YFKSIWNWLE LLLLLLCFVA VSFNTYYNVQ IFLLLGQLLK
360 370 380 390 400
STEKYSDFYF LACWHIYYNN IIAITIFFAW IKIFKFISFN KTMSQLSSTL
410 420 430 440 450
SRCVKDIVGF AIMFFIIFFA YAQLGFLVFG SQVDDFSTFQ NSIFAQFRIV
460 470 480 490 500
LGDFNFAGIQ QANPILGPIY FITFIFFVFF VLLNMFLAII NDTYSEVKAD
510 520 530 540 550
YSIGRRLDFE LGKMIKQSYK NVLEKFRLKK AQKDEDKKTK GSGDLAEQAR
560 570 580 590 600
REGFDENEIQ NAEQMKKWKE RLEKKYYSME IQDDYQPVTQ EEFRELFLYA
610 620
VELEKELHYI NLKLNQVVRK VSAL
Length:624
Mass (Da):73,790
Last modified:January 11, 2011 - v2
Checksum:i7D9FFA04542A47A4
GO
Isoform 2 (identifier: Q9NZM6-2) [UniParc]FASTAAdd to basket

Also known as: PKD2L2b

The sequence of this isoform differs from the canonical sequence as follows:
     11-44: Missing.
     45-45: L → V

Show »
Length:590
Mass (Da):69,746
Checksum:iBDDE4D9C3C3D7C5F
GO
Isoform 3 (identifier: Q9NZM6-3) [UniParc]FASTAAdd to basket

Also known as: PKD2L2a

The sequence of this isoform differs from the canonical sequence as follows:
     45-57: LTFGMVNPHMYYL → CYVISIFGHFCAW
     58-624: Missing.

Show »
Length:57
Mass (Da):6,759
Checksum:i4539353342C77CAA
GO
Isoform 4 (identifier: Q9NZM6-4) [UniParc]FASTAAdd to basket

Also known as: PKD2L2c

The sequence of this isoform differs from the canonical sequence as follows:
     12-23: ASKHKLHYRKEV → YVISIFGHFCAW
     24-624: Missing.

Show »
Length:23
Mass (Da):2,682
Checksum:i0C7B55E80C496CC0
GO
Isoform 5 (identifier: Q9NZM6-5) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     595-624: ELFLYAVELEKELHYINLKLNQVVRKVSAL → DGTTTKYKMRFSECLTKRI

Note: No experimental confirmation available.

Show »
Length:613
Mass (Da):72,496
Checksum:i198CD4B1F9EC9804
GO
Isoform 6 (identifier: Q9NZM6-6) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     383-483: Missing.

Note: No experimental confirmation available.

Show »
Length:523
Mass (Da):62,216
Checksum:i9D1CAFED503A7EF6
GO
Isoform 7 (identifier: Q9NZM6-7) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     326-347: Missing.

Note: No experimental confirmation available.

Show »
Length:602
Mass (Da):71,255
Checksum:iC409FD9113F83EB1
GO

Sequence cautioni

The sequence AAD46478.1 differs from that shown. Reason: Frameshift at position 595. Curated

Experimental Info

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sequence conflicti205 – 2062Missing in BAG63344 (PubMed:14702039).Curated

Natural variant

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Natural varianti404 – 4041V → I.1 Publication
Corresponds to variant rs1880458 [ dbSNP | Ensembl ].
VAR_047542
Natural varianti507 – 5071L → P.4 Publications
Corresponds to variant rs12187140 [ dbSNP | Ensembl ].
VAR_047543

Alternative sequence

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Alternative sequencei11 – 4434Missing in isoform 2. 1 PublicationVSP_004732Add
BLAST
Alternative sequencei12 – 2312ASKHK…YRKEV → YVISIFGHFCAW in isoform 4. 1 PublicationVSP_004733Add
BLAST
Alternative sequencei24 – 624601Missing in isoform 4. 1 PublicationVSP_004734Add
BLAST
Alternative sequencei45 – 5713LTFGM…HMYYL → CYVISIFGHFCAW in isoform 3. 1 PublicationVSP_004736Add
BLAST
Alternative sequencei45 – 451L → V in isoform 2. 1 PublicationVSP_004735
Alternative sequencei58 – 624567Missing in isoform 3. 1 PublicationVSP_004737Add
BLAST
Alternative sequencei326 – 34722Missing in isoform 7. 1 PublicationVSP_045581Add
BLAST
Alternative sequencei383 – 483101Missing in isoform 6. 1 PublicationVSP_045582Add
BLAST
Alternative sequencei595 – 62430ELFLY…KVSAL → DGTTTKYKMRFSECLTKRI in isoform 5. 1 PublicationVSP_035775Add
BLAST

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AF118125 mRNA. Translation: AAD46478.1. Frameshift.
AF182034 mRNA. Translation: AAF65622.1.
AC106753 Genomic DNA. No translation available.
AK301924 mRNA. Translation: BAG63344.1.
AC106791 Genomic DNA. No translation available.
CH471062 Genomic DNA. Translation: EAW62174.1.
BC044581 mRNA. Translation: AAH44581.1.
CCDSiCCDS43367.1. [Q9NZM6-5]
CCDS58971.1. [Q9NZM6-6]
CCDS58972.1. [Q9NZM6-7]
RefSeqiNP_001245377.1. NM_001258448.1. [Q9NZM6-7]
NP_001245378.1. NM_001258449.1. [Q9NZM6-6]
NP_001287850.1. NM_001300921.1. [Q9NZM6-1]
NP_055201.2. NM_014386.3. [Q9NZM6-5]
UniGeneiHs.716884.

Genome annotation databases

EnsembliENST00000290431; ENSP00000290431; ENSG00000078795. [Q9NZM6-5]
ENST00000414094; ENSP00000388060; ENSG00000078795. [Q9NZM6-3]
ENST00000502810; ENSP00000425513; ENSG00000078795. [Q9NZM6-7]
ENST00000508638; ENSP00000423382; ENSG00000078795. [Q9NZM6-6]
ENST00000508883; ENSP00000424725; ENSG00000078795. [Q9NZM6-1]
GeneIDi27039.
KEGGihsa:27039.
UCSCiuc003lbw.1. human. [Q9NZM6-5]
uc003lby.3. human. [Q9NZM6-1]

Keywords - Coding sequence diversityi

Alternative splicing, Polymorphism

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AF118125 mRNA. Translation: AAD46478.1. Frameshift.
AF182034 mRNA. Translation: AAF65622.1.
AC106753 Genomic DNA. No translation available.
AK301924 mRNA. Translation: BAG63344.1.
AC106791 Genomic DNA. No translation available.
CH471062 Genomic DNA. Translation: EAW62174.1.
BC044581 mRNA. Translation: AAH44581.1.
CCDSiCCDS43367.1. [Q9NZM6-5]
CCDS58971.1. [Q9NZM6-6]
CCDS58972.1. [Q9NZM6-7]
RefSeqiNP_001245377.1. NM_001258448.1. [Q9NZM6-7]
NP_001245378.1. NM_001258449.1. [Q9NZM6-6]
NP_001287850.1. NM_001300921.1. [Q9NZM6-1]
NP_055201.2. NM_014386.3. [Q9NZM6-5]
UniGeneiHs.716884.

3D structure databases

ProteinModelPortaliQ9NZM6.
SMRiQ9NZM6. Positions 408-492.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi117970. 4 interactions.
STRINGi9606.ENSP00000290431.

PTM databases

PhosphoSiteiQ9NZM6.

Polymorphism and mutation databases

BioMutaiPKD2L2.
DMDMi317373272.

Proteomic databases

PaxDbiQ9NZM6.
PRIDEiQ9NZM6.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000290431; ENSP00000290431; ENSG00000078795. [Q9NZM6-5]
ENST00000414094; ENSP00000388060; ENSG00000078795. [Q9NZM6-3]
ENST00000502810; ENSP00000425513; ENSG00000078795. [Q9NZM6-7]
ENST00000508638; ENSP00000423382; ENSG00000078795. [Q9NZM6-6]
ENST00000508883; ENSP00000424725; ENSG00000078795. [Q9NZM6-1]
GeneIDi27039.
KEGGihsa:27039.
UCSCiuc003lbw.1. human. [Q9NZM6-5]
uc003lby.3. human. [Q9NZM6-1]

Organism-specific databases

CTDi27039.
GeneCardsiGC05P137225.
H-InvDBHIX0024797.
HGNCiHGNC:9012. PKD2L2.
HPAiHPA041903.
HPA043634.
MIMi604669. gene.
neXtProtiNX_Q9NZM6.
PharmGKBiPA33345.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiNOG325704.
GeneTreeiENSGT00700000104221.
HOGENOMiHOG000230858.
HOVERGENiHBG014945.
InParanoidiQ9NZM6.
KOiK04991.
OMAiAQFRIVL.
OrthoDBiEOG7N8ZTW.
PhylomeDBiQ9NZM6.
TreeFamiTF316484.

Miscellaneous databases

GeneWikiiTRPP3.
GenomeRNAii27039.
NextBioi49604.
PROiQ9NZM6.
SOURCEiSearch...

Gene expression databases

BgeeiQ9NZM6.
CleanExiHS_PKD2L2.
ExpressionAtlasiQ9NZM6. baseline and differential.
GenevestigatoriQ9NZM6.

Family and domain databases

InterProiIPR013122. PKD1_2_channel.
IPR003915. PKD_2.
[Graphical view]
PfamiPF08016. PKD_channel. 1 hit.
[Graphical view]
PRINTSiPR01433. POLYCYSTIN2.
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "Genes homologous to the autosomal dominant polycystic kidney disease genes (PKD1 and PKD2)."
    Veldhuisen B., Spruit L., Dauwerse H.G., Breuning M.H., Peters D.J.M.
    Eur. J. Hum. Genet. 7:860-872(1999) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 5), VARIANT PRO-507.
    Tissue: Testis.
  2. "Identification and characterization of a novel polycystin family member, polycystin-L2, in mouse and human: sequence, expression, alternative splicing, and chromosomal localization."
    Guo L., Schreiber T.H., Weremowicz S., Morton C.C., Lee C., Zhou J.
    Genomics 64:241-251(2000) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORMS 1; 2; 3 AND 4), VARIANT PRO-507.
  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(2004) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA] (ISOFORM 7), VARIANTS ILE-404 AND PRO-507.
    Tissue: Testis.
  4. "The DNA sequence and comparative analysis of human chromosome 5."
    Schmutz J., Martin J., Terry A., Couronne O., Grimwood J., Lowry S., Gordon L.A., Scott D., Xie G., Huang W., Hellsten U., Tran-Gyamfi M., She X., Prabhakar S., Aerts A., Altherr M., Bajorek E., Black S.
    , Branscomb E., Caoile C., Challacombe J.F., Chan Y.M., Denys M., Detter J.C., Escobar J., Flowers D., Fotopulos D., Glavina T., Gomez M., Gonzales E., Goodstein D., Grigoriev I., Groza M., Hammon N., Hawkins T., Haydu L., Israni S., Jett J., Kadner K., Kimball H., Kobayashi A., Lopez F., Lou Y., Martinez D., Medina C., Morgan J., Nandkeshwar R., Noonan J.P., Pitluck S., Pollard M., Predki P., Priest J., Ramirez L., Retterer J., Rodriguez A., Rogers S., Salamov A., Salazar A., Thayer N., Tice H., Tsai M., Ustaszewska A., Vo N., Wheeler J., Wu K., Yang J., Dickson M., Cheng J.-F., Eichler E.E., Olsen A., Pennacchio L.A., Rokhsar D.S., Richardson P., Lucas S.M., Myers R.M., Rubin E.M.
    Nature 431:268-274(2004) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
  5. 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 6), VARIANT PRO-507.
    Tissue: Testis.
  7. Cited for: REVIEW.

Entry informationi

Entry nameiPK2L2_HUMAN
AccessioniPrimary (citable) accession number: Q9NZM6
Secondary accession number(s): A6NK98
, B4DXD2, E9PC91, E9PDG4, Q86YB4, Q9UNJ0
Entry historyi
Integrated into UniProtKB/Swiss-Prot: October 10, 2002
Last sequence update: January 11, 2011
Last modified: April 29, 2015
This is version 117 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

Complete proteome, Reference proteome

Documents

  1. Human chromosome 5
    Human chromosome 5: entries, gene names and cross-references to MIM
  2. Human entries with polymorphisms or disease mutations
    List of human entries with polymorphisms or disease mutations
  3. Human polymorphisms and disease mutations
    Index of human polymorphisms and disease mutations
  4. MIM cross-references
    Online Mendelian Inheritance in Man (MIM) cross-references in UniProtKB/Swiss-Prot
  5. 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.