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Protein

Protein unc-13 homolog A

Gene

Unc13a

Organism
Rattus norvegicus (Rat)
Status
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli

Functioni

Plays a role in vesicle maturation during exocytosis as a target of the diacylglycerol second messenger pathway. Involved in neurotransmitter release by acting in synaptic vesicle priming prior to vesicle fusion and participates in the activity-dependent refilling of readily releasable vesicle pool (RRP). Essential for synaptic vesicle maturation in most excitatory/glutamatergic but not inhibitory/GABA-mediated synapses. Also involved in secretory granule priming in insulin secretion. Plays a role in dendrite formation by melanocytes (By similarity).By similarity3 Publications

Sites

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Metal bindingi580Zinc 11
Metal bindingi583Zinc 11
Metal bindingi597Zinc 21
Metal bindingi600Zinc 21
Metal bindingi608Zinc 11
Metal bindingi616Zinc 21

Regions

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Zinc fingeri566 – 616Phorbol-ester/DAG-typePROSITE-ProRule annotationAdd BLAST51

GO - Molecular functioni

  • calmodulin binding Source: ParkinsonsUK-UCL
  • diacylglycerol binding Source: InterPro
  • metal ion binding Source: UniProtKB-KW
  • protein domain specific binding Source: RGD
  • protein heterodimerization activity Source: RGD
  • protein homodimerization activity Source: RGD
  • protein N-terminus binding Source: RGD
  • receptor activity Source: GO_Central
  • signal transducer activity Source: GO_Central
  • SNARE binding Source: RGD
  • spectrin binding Source: RGD
  • syntaxin-1 binding Source: ParkinsonsUK-UCL
  • syntaxin binding Source: ParkinsonsUK-UCL

GO - Biological processi

  • cell differentiation Source: UniProtKB-KW
  • intracellular signal transduction Source: InterPro
  • long-term synaptic potentiation Source: RGD
  • neurotransmitter secretion Source: RGD
  • synaptic vesicle priming Source: RGD
Complete GO annotation...

Keywords - Biological processi

Differentiation, Exocytosis

Keywords - Ligandi

Metal-binding, Zinc

Names & Taxonomyi

Protein namesi
Recommended name:
Protein unc-13 homolog A
Alternative name(s):
Munc13-1
Gene namesi
Name:Unc13a
Synonyms:Unc13h1
OrganismiRattus norvegicus (Rat)
Taxonomic identifieri10116 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresGliresRodentiaSciurognathiMuroideaMuridaeMurinaeRattus
Proteomesi
  • UP000002494 Componenti: Unplaced

Organism-specific databases

RGDi619722. Unc13a.

Subcellular locationi

GO - Cellular componenti

  • cell junction Source: UniProtKB-KW
  • cytoplasm Source: UniProtKB-SubCell
  • excitatory synapse Source: BHF-UCL
  • neuron projection Source: RGD
  • presynaptic active zone Source: GO_Central
  • presynaptic membrane Source: RGD
  • protein complex Source: RGD
  • synaptic membrane Source: ParkinsonsUK-UCL
  • terminal bouton Source: ParkinsonsUK-UCL
Complete GO annotation...

Keywords - Cellular componenti

Cell junction, Cell membrane, Cytoplasm, Membrane, Synapse

Pathology & Biotechi

Mutagenesis

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Mutagenesisi22T → I: No effect on binding to RIMS1. 1 Publication1
Mutagenesisi23Y → N: No effect on binding to RIMS1. 1 Publication1
Mutagenesisi64V → M: No effect on binding to RIMS1. 1 Publication1
Mutagenesisi119H → R: No effect on binding to RIMS1. 1 Publication1
Mutagenesisi121I → N: Abolishes binding to RIMS1. 1 Publication1
Mutagenesisi567H → K: Loss of phorbol-ester binding. 1 Publication1
Mutagenesisi1190Q → R: Loss of binding to STX1B and priming activity; when associated with P-1279 and E-1655. 1 Publication1
Mutagenesisi1279L → P: Loss of binding to STX1B and priming activity; when associated with R-1190 and E-1655. 1 Publication1
Mutagenesisi1364I → F: Loss of binding to STX1B and priming activity. 1 Publication1
Mutagenesisi1603V → D: Loss of binding to STX1B and priming activity. 1 Publication1
Mutagenesisi1655D → E: Loss of binding to STX1B and priming activity; when associated with R-1190 and P-1279. 1 Publication1

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
ChainiPRO_00001885741 – 1735Protein unc-13 homolog AAdd BLAST1735

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Modified residuei239PhosphoserineCombined sources1
Modified residuei241PhosphoserineCombined sources1
Modified residuei244PhosphoserineCombined sources1
Modified residuei255PhosphoserineCombined sources1

Keywords - PTMi

Phosphoprotein

Proteomic databases

PaxDbiQ62768.
PRIDEiQ62768.

PTM databases

iPTMnetiQ62768.
PhosphoSitePlusiQ62768.
SwissPalmiQ62768.

Expressioni

Tissue specificityi

Expressed in brain, with highest levels in the olfactory bulb, striatum, cerebral cortex, hippocampus and cerebellum. Also expressed in pancreatic islet cells.3 Publications

Developmental stagei

First detected at birth, after which expression level is steadily increasing until it reaches a plateau at P15.1 Publication

Interactioni

Subunit structurei

Interacts with the N-termini of STX1A and/or STX1B1 and DOC2A. Interacts with BSN. Interacts with RIMS1 which recruits UNC13A to the active zone. Forms homodimers via its first C2 domain. Also interacts via this domain with the zinc finger domain of RIMS2. Part of a complex consisting of ERC2, RIMS1 and UNC13A. Also part of a complex consisting of UNC13A, RIMS2 and RAB3A. Interacts with FBXO45 (via SRY domain); leading to the degradation of UNC13A by the proteasome (By similarity).By similarity

GO - Molecular functioni

  • calmodulin binding Source: ParkinsonsUK-UCL
  • protein domain specific binding Source: RGD
  • protein heterodimerization activity Source: RGD
  • protein homodimerization activity Source: RGD
  • protein N-terminus binding Source: RGD
  • SNARE binding Source: RGD
  • spectrin binding Source: RGD
  • syntaxin-1 binding Source: ParkinsonsUK-UCL
  • syntaxin binding Source: ParkinsonsUK-UCL

Protein-protein interaction databases

DIPiDIP-29191N.
STRINGi10116.ENSRNOP00000025162.

Structurei

Secondary structure

11735
Legend: HelixTurnBeta strandPDB Structure known for this area
Show more details
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Beta strandi2 – 12Combined sources11
Helixi17 – 19Combined sources3
Beta strandi21 – 28Combined sources8
Beta strandi31 – 34Combined sources4
Beta strandi38 – 42Combined sources5
Beta strandi44 – 53Combined sources10
Beta strandi57 – 66Combined sources10
Beta strandi72 – 81Combined sources10
Helixi82 – 84Combined sources3
Beta strandi95 – 98Combined sources4
Beta strandi102 – 106Combined sources5
Beta strandi109 – 111Combined sources3
Beta strandi120 – 128Combined sources9
Helixi135 – 150Combined sources16
Helixi459 – 478Combined sources20
Helixi487 – 490Combined sources4
Beta strandi569 – 573Combined sources5
Turni581 – 583Combined sources3
Beta strandi593 – 597Combined sources5
Turni598 – 600Combined sources3
Helixi608 – 611Combined sources4
Beta strandi689 – 700Combined sources12
Beta strandi712 – 718Combined sources7
Beta strandi721 – 724Combined sources4
Beta strandi735 – 744Combined sources10
Beta strandi750 – 757Combined sources8
Helixi762 – 767Combined sources6
Turni768 – 770Combined sources3
Beta strandi774 – 784Combined sources11
Helixi785 – 787Combined sources3
Beta strandi790 – 797Combined sources8
Beta strandi810 – 818Combined sources9
Helixi943 – 961Combined sources19
Helixi964 – 967Combined sources4
Helixi973 – 995Combined sources23
Helixi1005 – 1026Combined sources22
Helixi1028 – 1035Combined sources8
Beta strandi1039 – 1041Combined sources3
Beta strandi1051 – 1053Combined sources3
Helixi1059 – 1077Combined sources19
Helixi1079 – 1082Combined sources4
Turni1087 – 1089Combined sources3
Helixi1092 – 1118Combined sources27
Helixi1123 – 1140Combined sources18
Turni1141 – 1143Combined sources3
Helixi1145 – 1148Combined sources4
Helixi1159 – 1187Combined sources29
Beta strandi1192 – 1195Combined sources4
Helixi1201 – 1218Combined sources18
Helixi1224 – 1256Combined sources33
Helixi1259 – 1261Combined sources3
Helixi1263 – 1285Combined sources23
Turni1286 – 1290Combined sources5
Helixi1293 – 1320Combined sources28
Helixi1322 – 1337Combined sources16
Helixi1353 – 1378Combined sources26
Helixi1381 – 1402Combined sources22
Beta strandi1454 – 1456Combined sources3
Beta strandi1458 – 1461Combined sources4
Helixi1472 – 1487Combined sources16
Helixi1488 – 1490Combined sources3
Helixi1495 – 1499Combined sources5
Helixi1502 – 1513Combined sources12
Turni1516 – 1518Combined sources3

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
1Y8FNMR-A567-616[»]
2CJSX-ray1.78A/B2-150[»]
2CJTX-ray1.44A/B/C/D1-128[»]
2KDUNMR-B458-492[»]
3KWTX-ray1.89A675-820[»]
3KWUX-ray1.37A675-820[»]
3SWHX-ray2.65A/B1148-1407[»]
A/B1453-1531[»]
4Y21X-ray2.90A942-1407[»]
A1453-1523[»]
ProteinModelPortaliQ62768.
SMRiQ62768.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiQ62768.

Family & Domainsi

Domains and Repeats

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Domaini1 – 79C2 1PROSITE-ProRule annotationAdd BLAST79
Domaini676 – 782C2 2PROSITE-ProRule annotationAdd BLAST107
Domaini1106 – 1249MHD1PROSITE-ProRule annotationAdd BLAST144
Domaini1358 – 1525MHD2PROSITE-ProRule annotationAdd BLAST168
Domaini1564 – 1691C2 3PROSITE-ProRule annotationAdd BLAST128

Coiled coil

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Coiled coili319 – 370Sequence analysisAdd BLAST52

Compositional bias

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Compositional biasi320 – 452Glu-richAdd BLAST133

Domaini

The C2 domains are not involved in calcium-dependent phospholipid binding.1 Publication
The C-terminal region containing both MHD domains and the third C2 domain is required for synaptic vesicle priming activity.1 Publication

Sequence similaritiesi

Belongs to the unc-13 family.Curated
Contains 3 C2 domains.PROSITE-ProRule annotation
Contains 1 MHD1 (MUNC13 homology domain 1) domain.PROSITE-ProRule annotation
Contains 1 MHD2 (MUNC13 homology domain 2) domain.PROSITE-ProRule annotation
Contains 1 phorbol-ester/DAG-type zinc finger.PROSITE-ProRule annotation

Zinc finger

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Zinc fingeri566 – 616Phorbol-ester/DAG-typePROSITE-ProRule annotationAdd BLAST51

Keywords - Domaini

Coiled coil, Repeat, Zinc-finger

Phylogenomic databases

eggNOGiKOG1011. Eukaryota.
ENOG410XS5D. LUCA.
HOVERGENiHBG057340.
InParanoidiQ62768.
KOiK15293.
PhylomeDBiQ62768.

Family and domain databases

CDDicd00029. C1. 1 hit.
Gene3Di2.60.40.150. 3 hits.
InterProiIPR000008. C2_dom.
IPR010439. CAPS_dom.
IPR014770. Munc13_1.
IPR014772. Munc13_dom-2.
IPR019558. Munc13_subgr_dom-2.
IPR002219. PE/DAG-bd.
IPR027080. Unc-13.
[Graphical view]
PANTHERiPTHR10480. PTHR10480. 3 hits.
PfamiPF00130. C1_1. 1 hit.
PF00168. C2. 3 hits.
PF06292. DUF1041. 1 hit.
PF10540. Membr_traf_MHD. 1 hit.
[Graphical view]
SMARTiSM00109. C1. 1 hit.
SM00239. C2. 3 hits.
SM01145. DUF1041. 1 hit.
[Graphical view]
SUPFAMiSSF49562. SSF49562. 3 hits.
PROSITEiPS50004. C2. 2 hits.
PS51258. MHD1. 1 hit.
PS51259. MHD2. 1 hit.
PS00479. ZF_DAG_PE_1. 1 hit.
PS50081. ZF_DAG_PE_2. 1 hit.
[Graphical view]

Sequences (3)i

Sequence statusi: Complete.

This entry describes 3 isoformsi produced by alternative splicing. AlignAdd to basket

Isoform 1 (identifier: Q62768-1) [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
MSLLCVGVKK AKFDGAQEKF NTYVTLKVQN VKSTTIAVRG SQPSWEQDFM
60 70 80 90 100
FEINRLDLGL TVEVWNKGLI WDTMVGTVWI PLRTIRQSNE EGPGEWLTLD
110 120 130 140 150
SQAIMADSEI CGTKDPTFHR ILLDAHFELP LDIPEEEARY WAKKLEQLNA
160 170 180 190 200
MRDQDEYSFQ DQQDKPLPVP SSQCCNWNYF GWGEQNDDPD SAVDDRDSDY
210 220 230 240 250
RSETSNSIPP PYYTTSQPNA SVHQYSVRPP PLGSRESYSD SMHSYEEFSE
260 270 280 290 300
PRALSPTGSS RYASSGELSQ GSSQLSEDFD PDEHSLQGSE LDDERDRDSY
310 320 330 340 350
HSCHSSVSYH KDSPRWDQDE EDLEDLEDLE DEELPEEEEL EEEELEEEEE
360 370 380 390 400
LEEEELELEE EEEVPDDLAS YTQQEDTTVA EPKEFKRISF PTAAPQKEDK
410 420 430 440 450
VSAVPIEAPD VSKGIPKAAT PEEKAAAECA QEAEPPKSEE SFRSREAEEG
460 470 480 490 500
QEGQDAMSRA KANWLRAFNK VRMQLQEARG EGEMSKSLWF KGGPGGGLII
510 520 530 540 550
IDSMPDIRKR KPIPLVSDLA MSLVQSRKAG ITSALASSTL NNEELKNHVY
560 570 580 590 600
KKTLQALIYP ISCTTPHNFE VWTATTPTYC YECEGLLWGI ARQGMRCTEC
610 620 630 640 650
GVKCHEKCQD LLNADCLQRA AEKSSKHGAE DRTQNIIMVL KDRMKIRERN
660 670 680 690 700
KPEIFELIQE VFAVTKSAHT QQMKAVKQSV LDGTSKWSAK ISITVVCAQG
710 720 730 740 750
LQAKDKTGSS DPYVTVQVGK TKKRTKTIYG NLNPVWEENF HFECHNSSDR
760 770 780 790 800
IKVRVLDEDD DIKSRVKQRF KRESDDFLGQ TIIEVRTLSG EMDVWYNLDK
810 820 830 840 850
RTDKSAVSGA IRLHISVEIK GEEKVAPYHV QYTCLHENLF HFVTDVQNNG
860 870 880 890 900
VVKIPDAKGD DAWKVYYDET AQEIVDEFAM RYGVESIYQA MTHFACLSSK
910 920 930 940 950
YMCPGVPAVM STLLANINAY YAHTTASTNV SASDRFAASN FGKERFVKLL
960 970 980 990 1000
DQLHNSLRID LSMYRNNFPA SSPERLQDLK STVDLLTSIT FFRMKVQELQ
1010 1020 1030 1040 1050
SPPRASQVVK DCVKACLNST YEYIFNNCHE LYGREYQTDP AKKGEVPPEE
1060 1070 1080 1090 1100
QGPSIKNLDF WSKLITLIVS IIEEDKNSYT PCLNQFPQEL NVGKISAEVM
1110 1120 1130 1140 1150
WSLFAQDMKY AMEEHDKHRL CKSADYMNLH FKVKWLYNEY VAELPTFKDR
1160 1170 1180 1190 1200
VPEYPAWFEP FVIQWLDENE EVSRDFLHGA LERDKKDGFQ QTSEHALFSC
1210 1220 1230 1240 1250
SVVDVFSQLN QSFEIIKKLE CPDPQIVGHY MRRFAKTISN VLLQYADIVS
1260 1270 1280 1290 1300
KDFASYCSKE KEKVPCILMN NTQQLRVQLE KMFEAMGGKE LDAEASGTLK
1310 1320 1330 1340 1350
ELQVKLNNVL DELSHVFATS FQPHIEECVR QMGDILSQVK GTGNVPASAC
1360 1370 1380 1390 1400
SSVAQDADNV LQPIMDLLDS NLTLFAKICE KTVLKRVLKE LWKLVMNTME
1410 1420 1430 1440 1450
RTIVLPPLTD QTMIGTLLRK HGKGLEKGRV KLPSHSDGTQ MIFNAAKELG
1460 1470 1480 1490 1500
QLSKLKDHMV REEAKSLTPK QCAVVELALD TIKQYFHAGG VGLKKTFLEK
1510 1520 1530 1540 1550
SPDLQSLRYA LSLYTQATDL LIKTFVQTQS AQVHGGKGTR FTLSEDVCPE
1560 1570 1580 1590 1600
MGSGVEDPVG EVSVHVELFT HPGTGEQKVT VKVVAANDLK WQTSGIFRPF
1610 1620 1630 1640 1650
IEVNIVGPQL SDKKRKFATK SKNNSWAPKY NESFQFSLSA DAGPECYELQ
1660 1670 1680 1690 1700
VCVKDYCFAR EDRTVELAVL QLRELAQRGS AACWLPLGRR IHMDDTGLTV
1710 1720 1730
LRILSQRSND EVAKEFVKLK SDTRSAEEGG AAPAP
Length:1,735
Mass (Da):196,356
Last modified:November 1, 1996 - v1
Checksum:iBFE7D0467D258900
GO
Isoform 2 (identifier: Q62768-2) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     1434-1456: Missing.

Show »
Length:1,712
Mass (Da):193,870
Checksum:i567EDEFA1D78F775
GO
Isoform 3 (identifier: Q62768-3) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     1541-1559: Missing.

Show »
Length:1,716
Mass (Da):194,363
Checksum:i2F917D1CE8A33D1E
GO

Alternative sequence

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Alternative sequenceiVSP_0113821434 – 1456Missing in isoform 2. CuratedAdd BLAST23
Alternative sequenceiVSP_0113831541 – 1559Missing in isoform 3. CuratedAdd BLAST19

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
U24070 mRNA. Translation: AAC52266.1.
PIRiA57607.
RefSeqiNP_074052.1. NM_022861.1. [Q62768-1]
UniGeneiRn.10126.

Genome annotation databases

GeneIDi64829.
KEGGirno:64829.

Keywords - Coding sequence diversityi

Alternative splicing

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
U24070 mRNA. Translation: AAC52266.1.
PIRiA57607.
RefSeqiNP_074052.1. NM_022861.1. [Q62768-1]
UniGeneiRn.10126.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
1Y8FNMR-A567-616[»]
2CJSX-ray1.78A/B2-150[»]
2CJTX-ray1.44A/B/C/D1-128[»]
2KDUNMR-B458-492[»]
3KWTX-ray1.89A675-820[»]
3KWUX-ray1.37A675-820[»]
3SWHX-ray2.65A/B1148-1407[»]
A/B1453-1531[»]
4Y21X-ray2.90A942-1407[»]
A1453-1523[»]
ProteinModelPortaliQ62768.
SMRiQ62768.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

DIPiDIP-29191N.
STRINGi10116.ENSRNOP00000025162.

PTM databases

iPTMnetiQ62768.
PhosphoSitePlusiQ62768.
SwissPalmiQ62768.

Proteomic databases

PaxDbiQ62768.
PRIDEiQ62768.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

GeneIDi64829.
KEGGirno:64829.

Organism-specific databases

CTDi23025.
RGDi619722. Unc13a.

Phylogenomic databases

eggNOGiKOG1011. Eukaryota.
ENOG410XS5D. LUCA.
HOVERGENiHBG057340.
InParanoidiQ62768.
KOiK15293.
PhylomeDBiQ62768.

Miscellaneous databases

EvolutionaryTraceiQ62768.
PROiQ62768.

Family and domain databases

CDDicd00029. C1. 1 hit.
Gene3Di2.60.40.150. 3 hits.
InterProiIPR000008. C2_dom.
IPR010439. CAPS_dom.
IPR014770. Munc13_1.
IPR014772. Munc13_dom-2.
IPR019558. Munc13_subgr_dom-2.
IPR002219. PE/DAG-bd.
IPR027080. Unc-13.
[Graphical view]
PANTHERiPTHR10480. PTHR10480. 3 hits.
PfamiPF00130. C1_1. 1 hit.
PF00168. C2. 3 hits.
PF06292. DUF1041. 1 hit.
PF10540. Membr_traf_MHD. 1 hit.
[Graphical view]
SMARTiSM00109. C1. 1 hit.
SM00239. C2. 3 hits.
SM01145. DUF1041. 1 hit.
[Graphical view]
SUPFAMiSSF49562. SSF49562. 3 hits.
PROSITEiPS50004. C2. 2 hits.
PS51258. MHD1. 1 hit.
PS51259. MHD2. 1 hit.
PS00479. ZF_DAG_PE_1. 1 hit.
PS50081. ZF_DAG_PE_2. 1 hit.
[Graphical view]
ProtoNetiSearch...

Entry informationi

Entry nameiUN13A_RAT
AccessioniPrimary (citable) accession number: Q62768
Entry historyi
Integrated into UniProtKB/Swiss-Prot: August 16, 2004
Last sequence update: November 1, 1996
Last modified: November 30, 2016
This is version 128 of the entry and version 1 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programChordata Protein Annotation Program

Miscellaneousi

Keywords - Technical termi

3D-structure, Complete proteome, Reference proteome

Documents

  1. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  2. 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.