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Protein

Protein unc-13 homolog B

Gene

Unc13b

Organism
Mus musculus (Mouse)
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. Is involved in neurotransmitter release by acting in synaptic vesicle priming prior to vesicle fusion and participates in the activity-depending refilling of readily releasable vesicle pool (RRP) (By similarity). Essential for synaptic vesicle maturation in a subset of excitatory/glutamatergic but not inhibitory/GABA-mediated synapses.By similarity1 Publication

Regions

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Zinc fingeri489 – 53951Phorbol-ester/DAG-typePROSITE-ProRule annotationAdd
BLAST

GO - Molecular functioni

  • diacylglycerol binding Source: InterPro
  • metal ion binding Source: UniProtKB-KW
  • non-kinase phorbol ester receptor activity Source: MGI

GO - Biological processi

  • innervation Source: MGI
  • intracellular signal transduction Source: InterPro
  • neuromuscular junction development Source: MGI
  • positive regulation of inhibitory postsynaptic potential Source: ParkinsonsUK-UCL
  • positive regulation of synaptic vesicle priming Source: ParkinsonsUK-UCL
  • regulation of short-term neuronal synaptic plasticity Source: MGI
  • synaptic transmission Source: MGI
  • synaptic transmission, glutamatergic Source: MGI
  • synaptic vesicle docking Source: MGI
  • synaptic vesicle priming Source: MGI
Complete GO annotation...

Keywords - Biological processi

Exocytosis

Keywords - Ligandi

Metal-binding, Zinc

Enzyme and pathway databases

ReactomeiR-MMU-181430. Norepinephrine Neurotransmitter Release Cycle.
R-MMU-210500. Glutamate Neurotransmitter Release Cycle.
R-MMU-264642. Acetylcholine Neurotransmitter Release Cycle.

Names & Taxonomyi

Protein namesi
Recommended name:
Protein unc-13 homolog B
Alternative name(s):
Munc13-2
Short name:
munc13
Gene namesi
Name:Unc13b
Synonyms:Unc13a
OrganismiMus musculus (Mouse)
Taxonomic identifieri10090 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresGliresRodentiaSciurognathiMuroideaMuridaeMurinaeMusMus
Proteomesi
  • UP000000589 Componenti: Chromosome 4

Organism-specific databases

MGIiMGI:1342278. Unc13b.

Subcellular locationi

GO - Cellular componenti

  • cell junction Source: UniProtKB-KW
  • cytosol Source: MGI
  • Golgi apparatus Source: MGI
  • neuromuscular junction Source: MGI
  • plasma membrane Source: ParkinsonsUK-UCL
  • terminal bouton Source: ParkinsonsUK-UCL
Complete GO annotation...

Keywords - Cellular componenti

Cell junction, Cytoplasm, Golgi apparatus, Membrane, Synapse

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Chaini1 – 16021602Protein unc-13 homolog BPRO_0000188576Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei16 – 161PhosphoserineBy similarity
Modified residuei307 – 3071PhosphoserineBy similarity
Modified residuei379 – 3791PhosphoserineBy similarity

Keywords - PTMi

Phosphoprotein

Proteomic databases

EPDiQ9Z1N9.
MaxQBiQ9Z1N9.
PaxDbiQ9Z1N9.
PRIDEiQ9Z1N9.

PTM databases

iPTMnetiQ9Z1N9.
PhosphoSiteiQ9Z1N9.

Expressioni

Gene expression databases

BgeeiQ9Z1N9.
CleanExiMM_UNC13A.
MM_UNC13B.
ExpressionAtlasiQ9Z1N9. baseline and differential.
GenevisibleiQ9Z1N9. MM.

Interactioni

Subunit structurei

Interacts with RIMS1.By similarity

Protein-protein interaction databases

STRINGi10090.ENSMUSP00000103586.

Structurei

3D structure databases

ProteinModelPortaliQ9Z1N9.
SMRiQ9Z1N9. Positions 2-128, 490-539, 610-742, 865-1414.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Domains and Repeats

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Domaini1 – 7979C2 1PROSITE-ProRule annotationAdd
BLAST
Domaini599 – 705107C2 2PROSITE-ProRule annotationAdd
BLAST
Domaini1024 – 1168145MHD1PROSITE-ProRule annotationAdd
BLAST
Domaini1275 – 1417143MHD2PROSITE-ProRule annotationAdd
BLAST
Domaini1437 – 1542106C2 3PROSITE-ProRule annotationAdd
BLAST

Coiled coil

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Coiled coili1210 – 123122Sequence analysisAdd
BLAST

Domaini

The C2 domains are not involved in calcium-dependent phospholipid binding.By similarity

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)LengthDescriptionGraphical viewFeature identifierActions
Zinc fingeri489 – 53951Phorbol-ester/DAG-typePROSITE-ProRule annotationAdd
BLAST

Keywords - Domaini

Coiled coil, Repeat, Zinc-finger

Phylogenomic databases

eggNOGiKOG1011. Eukaryota.
ENOG410XS5D. LUCA.
GeneTreeiENSGT00730000110590.
HOGENOMiHOG000231404.
HOVERGENiHBG057340.
InParanoidiQ9Z1N9.
KOiK15293.
OrthoDBiEOG76738V.
PhylomeDBiQ9Z1N9.
TreeFamiTF312844.

Family and domain databases

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. 1 hit.
PfamiPF00130. C1_1. 1 hit.
PF00168. C2. 3 hits.
PF06292. DUF1041. 1 hit.
PF10540. Membr_traf_MHD. 1 hit.
[Graphical view]
PRINTSiPR00360. C2DOMAIN.
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: Q9Z1N9-1) [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
MSLLCVRVKR AKFQGSPDKF NTYVTLKVQN VKSTTVAVRG DQPSWEQDFM
60 70 80 90 100
FEISRLDLGL SVEVWNKGLI WDTMVGTVWI ALKTIRQSDE EGPGEWSTLE
110 120 130 140 150
AETLMKDDEI CGTKNPTPHK ILLDTRFELP FDIPEEEARY WTYKLEQINA
160 170 180 190 200
LADDNEYSSQ EESQRKPLPT AAAQCCHWTY LGWGEHQTFE DPDSAVDDRD
210 220 230 240 250
SDYRSETSNS APPPYHTTTQ PNASVHQFPV PVRLPQQLFL QGSSHDSCND
260 270 280 290 300
SMQSYDLDYP ERRALSPTSS SRYGSSCNVS QGSSLLSELD QYHEQDDDGR
310 320 330 340 350
ERDSIHSSHS YGSLSKDGQA GLGEQEKALE VTCESEKEKT GESKEMRDDA
360 370 380 390 400
TIHPPSDLVL HKDHVLGPQE SLPEETASSP FTQARAHWFR AVTKVRLQLQ
410 420 430 440 450
EISDDGDPSL PQWLPEGPAG GLYGIDSMPD LRRKKPLPLV SDLSLVQSRK
460 470 480 490 500
AGITSAMATR TSLKDEELKS HVYKKTLQAL IYPISCTTPH NFEVWSATTP
510 520 530 540 550
TYCYECEGLL WGLARQGMRC SECGVKCHEK CQDLLNADCL QRAAEKSSKH
560 570 580 590 600
GAEDRTQNII MAMKDRMKIR ERNKPEIFEV IRDVFTVSKV AHVQQMKTVK
610 620 630 640 650
QSVLDGTSKW SAKITITVVC AQGLQAKDKT GSSDPYVTVQ VGKTKKRTKT
660 670 680 690 700
IFGNLNPVWE EKFHFECHNS SDRIKVRVWD EDDDIKSRVK QRLKRESDDF
710 720 730 740 750
LGQTIIEVRT LSGEMDVWYN LEKRTDKSAV SGAIRLQISV EIKGEEKVAP
760 770 780 790 800
YHVQYTCLHE NLFHYLTDIQ GSGGVWIPEA RGDDAWKVYF DETAQEIVDE
810 820 830 840 850
FAMRYGIESI YQAMTHFACL SSKYMCPGVP AVMSTLLANI NAYYAHTTAS
860 870 880 890 900
TNVSASDRFA ASNFGKERFV KLLDQLHNSL RIDLSTYRNN FPAGSPERLQ
910 920 930 940 950
DLKSTVDLLT SITFFRMKVQ ELQSPPRASQ VVKDCVKACL NSTYEYIFNN
960 970 980 990 1000
CHDLYSHQYQ LQEQPLEEPG PSIRNLDFWP KLITLIVSII EEDKNSYTPV
1010 1020 1030 1040 1050
LSQFPQELNV GKVSAEVMWH LFAQDMKYAL EEHEKDRLCK SADYMNLHFK
1060 1070 1080 1090 1100
VKWLHNEYVR DLPALQGQVP EYPAWFEQFV LQWLDENEDV SLEFLRGALE
1110 1120 1130 1140 1150
RDKKDGFQQT SEHALFSCSV VDVFTQLNQS FEIIRKLECP DPNILAHYMR
1160 1170 1180 1190 1200
RFAKTIGKVL MQYADILSKN FPAYCTKERL PCILMNNMQQ LRVQLEKMFE
1210 1220 1230 1240 1250
AMGGKELDSE AADSLKELQV KLNTVLDELS MVFGNSFQVR IDECVRQMAD
1260 1270 1280 1290 1300
ILGQVRGTGN ASPNARASVA QDADSVLRPL MDFLDGNLTL FATVCEKTVL
1310 1320 1330 1340 1350
KRVLKELWRV VMNTMERVIV LPPLTDQTGT QLILTAAKEL SQLSKLKDHM
1360 1370 1380 1390 1400
VREETRNLTP KQCAVLDLAL DTIKQYFHAG GNGLKKTFLE KSPDLQSLRY
1410 1420 1430 1440 1450
ALSLYTQTTD TLIKTFVRSQ TAQGAGVDDP VGEVSIQVDL FTHPGTGEHK
1460 1470 1480 1490 1500
VTVKVVAAND LKWQTAGMFR PFVEVTMVGP HQSDKKRKFT TKSKSNNWTP
1510 1520 1530 1540 1550
KYNETFHFLL GNEEGPEAYE LQICVKDYCF AREDRVIGLA VMPLRDVAAK
1560 1570 1580 1590 1600
GSCACWCPLG RKIHMDETGM TILRILSQRS NDEVAREFVK LKSESRSTEE

GS
Length:1,602
Mass (Da):181,813
Last modified:May 18, 2010 - v2
Checksum:iFED63BFE566554D2
GO
Isoform 2 (identifier: Q9Z1N9-2) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     176-188: CHWTYLGWGEHQT → S

Show »
Length:1,590
Mass (Da):180,300
Checksum:iD686E2CE66FA2D6B
GO
Isoform 3 (identifier: Q9Z1N9-3) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     962-962: Missing.

Show »
Length:1,601
Mass (Da):181,685
Checksum:iC17F209366F018CE
GO

Experimental Info

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sequence conflicti31 – 311V → E in AAD13619 (Ref. 2) Curated
Sequence conflicti208 – 2081S → D in AAD13619 (Ref. 2) Curated
Sequence conflicti234 – 2341L → W in BAD32690 (PubMed:15330860).Curated
Sequence conflicti234 – 2341L → W in AAD13619 (Ref. 2) Curated
Sequence conflicti262 – 2621R → H in AAD13619 (Ref. 2) Curated
Sequence conflicti353 – 3531H → Y in BAD32690 (PubMed:15330860).Curated
Sequence conflicti353 – 3531H → Y in AAD13619 (Ref. 2) Curated
Sequence conflicti512 – 5132GL → AV in BAD32690 (PubMed:15330860).Curated
Sequence conflicti512 – 5132GL → AV in AAD13619 (Ref. 2) Curated
Sequence conflicti579 – 5802EV → RI in AAD13619 (Ref. 2) Curated
Sequence conflicti804 – 8041R → A in AAD13619 (Ref. 2) Curated
Sequence conflicti837 – 8371L → M in AAD13619 (Ref. 2) Curated
Sequence conflicti1073 – 10731P → PG in AAD13619 (Ref. 2) Curated
Sequence conflicti1279 – 12802PL → GV in AAD13619 (Ref. 2) Curated
Sequence conflicti1280 – 12801L → P in AAI58026 (Ref. 2) Curated
Sequence conflicti1418 – 14181R → G in AAD13619 (Ref. 2) Curated
Sequence conflicti1492 – 14921K → R in AAD13619 (Ref. 2) Curated

Alternative sequence

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Alternative sequencei176 – 18813CHWTY…GEHQT → S in isoform 2. 1 PublicationVSP_039197Add
BLAST
Alternative sequencei962 – 9621Missing in isoform 3. 1 PublicationVSP_039198

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AB162894 Genomic DNA. Translation: BAD32690.1.
AF115848 mRNA. Translation: AAD13619.1.
AL672276, AL732504, AL772176 Genomic DNA. Translation: CAM14326.1.
AL732504, AL672276, AL772176 Genomic DNA. Translation: CAM16530.1.
AL772176, AL672276, AL732504 Genomic DNA. Translation: CAM22579.1.
BC157967 mRNA. Translation: AAI57968.1.
BC158025 mRNA. Translation: AAI58026.1.
CCDSiCCDS38738.1. [Q9Z1N9-3]
CCDS51161.1. [Q9Z1N9-1]
CCDS80089.1. [Q9Z1N9-2]
RefSeqiNP_001074882.1. NM_001081413.2. [Q9Z1N9-3]
NP_001297687.1. NM_001310758.1. [Q9Z1N9-2]
NP_067443.2. NM_021468.3. [Q9Z1N9-1]
UniGeneiMm.128892.

Genome annotation databases

EnsembliENSMUST00000079978; ENSMUSP00000078894; ENSMUSG00000028456. [Q9Z1N9-2]
ENSMUST00000107952; ENSMUSP00000103586; ENSMUSG00000028456. [Q9Z1N9-1]
ENSMUST00000163653; ENSMUSP00000128608; ENSMUSG00000028456. [Q9Z1N9-3]
GeneIDi22249.
KEGGimmu:22249.
UCSCiuc008spg.2. mouse. [Q9Z1N9-3]
uc012dcy.1. mouse. [Q9Z1N9-1]

Keywords - Coding sequence diversityi

Alternative splicing

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AB162894 Genomic DNA. Translation: BAD32690.1.
AF115848 mRNA. Translation: AAD13619.1.
AL672276, AL732504, AL772176 Genomic DNA. Translation: CAM14326.1.
AL732504, AL672276, AL772176 Genomic DNA. Translation: CAM16530.1.
AL772176, AL672276, AL732504 Genomic DNA. Translation: CAM22579.1.
BC157967 mRNA. Translation: AAI57968.1.
BC158025 mRNA. Translation: AAI58026.1.
CCDSiCCDS38738.1. [Q9Z1N9-3]
CCDS51161.1. [Q9Z1N9-1]
CCDS80089.1. [Q9Z1N9-2]
RefSeqiNP_001074882.1. NM_001081413.2. [Q9Z1N9-3]
NP_001297687.1. NM_001310758.1. [Q9Z1N9-2]
NP_067443.2. NM_021468.3. [Q9Z1N9-1]
UniGeneiMm.128892.

3D structure databases

ProteinModelPortaliQ9Z1N9.
SMRiQ9Z1N9. Positions 2-128, 490-539, 610-742, 865-1414.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

STRINGi10090.ENSMUSP00000103586.

PTM databases

iPTMnetiQ9Z1N9.
PhosphoSiteiQ9Z1N9.

Proteomic databases

EPDiQ9Z1N9.
MaxQBiQ9Z1N9.
PaxDbiQ9Z1N9.
PRIDEiQ9Z1N9.

Protocols and materials databases

DNASUi22249.
Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENSMUST00000079978; ENSMUSP00000078894; ENSMUSG00000028456. [Q9Z1N9-2]
ENSMUST00000107952; ENSMUSP00000103586; ENSMUSG00000028456. [Q9Z1N9-1]
ENSMUST00000163653; ENSMUSP00000128608; ENSMUSG00000028456. [Q9Z1N9-3]
GeneIDi22249.
KEGGimmu:22249.
UCSCiuc008spg.2. mouse. [Q9Z1N9-3]
uc012dcy.1. mouse. [Q9Z1N9-1]

Organism-specific databases

CTDi10497.
MGIiMGI:1342278. Unc13b.

Phylogenomic databases

eggNOGiKOG1011. Eukaryota.
ENOG410XS5D. LUCA.
GeneTreeiENSGT00730000110590.
HOGENOMiHOG000231404.
HOVERGENiHBG057340.
InParanoidiQ9Z1N9.
KOiK15293.
OrthoDBiEOG76738V.
PhylomeDBiQ9Z1N9.
TreeFamiTF312844.

Enzyme and pathway databases

ReactomeiR-MMU-181430. Norepinephrine Neurotransmitter Release Cycle.
R-MMU-210500. Glutamate Neurotransmitter Release Cycle.
R-MMU-264642. Acetylcholine Neurotransmitter Release Cycle.

Miscellaneous databases

PROiQ9Z1N9.
SOURCEiSearch...

Gene expression databases

BgeeiQ9Z1N9.
CleanExiMM_UNC13A.
MM_UNC13B.
ExpressionAtlasiQ9Z1N9. baseline and differential.
GenevisibleiQ9Z1N9. MM.

Family and domain databases

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. 1 hit.
PfamiPF00130. C1_1. 1 hit.
PF00168. C2. 3 hits.
PF06292. DUF1041. 1 hit.
PF10540. Membr_traf_MHD. 1 hit.
[Graphical view]
PRINTSiPR00360. C2DOMAIN.
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...

Publicationsi

« Hide 'large scale' publications
  1. "Alternative splicing in the first alpha-helical region of the Rab-binding domain of Rim regulates Rab3A binding activity: is Rim a Rab3 effector protein during evolution?"
    Fukuda M.
    Genes Cells 9:831-842(2004) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA], ALTERNATIVE SPLICING (ISOFORM 2).
    Strain: BALB/cJ.
  2. "Cloning of the mouse renal isoform of munc13s."
    Song Y., Silverman M.
    Submitted (DEC-1998) to the EMBL/GenBank/DDBJ databases
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 2).
    Strain: C57BL/6J.
  3. Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    Strain: C57BL/6J.
  4. "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] (ISOFORMS 1 AND 3).
  5. "Total arrest of spontaneous and evoked synaptic transmission but normal synaptogenesis in the absence of Munc13-mediated vesicle priming."
    Varoqueaux F., Sigler A., Rhee J.-S., Brose N., Enk C., Reim K., Rosenmund C.
    Proc. Natl. Acad. Sci. U.S.A. 99:9037-9042(2002) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION.
  6. Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
    Tissue: Lung.

Entry informationi

Entry nameiUN13B_MOUSE
AccessioniPrimary (citable) accession number: Q9Z1N9
Secondary accession number(s): A2AG43
, B2RXT0, B2RXY6, Q6BCX2
Entry historyi
Integrated into UniProtKB/Swiss-Prot: August 16, 2004
Last sequence update: May 18, 2010
Last modified: July 6, 2016
This is version 130 of the entry and version 2 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programChordata Protein Annotation Program

Miscellaneousi

Keywords - Technical termi

Complete proteome, Reference proteome

Documents

  1. MGD cross-references
    Mouse Genome Database (MGD) cross-references in UniProtKB/Swiss-Prot
  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.