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Protein

Gem-associated protein 2

Gene

GEMIN2

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

Functioni

The SMN complex plays a catalyst role in the assembly of small nuclear ribonucleoproteins (snRNPs), the building blocks of the spliceosome. Thereby, plays an important role in the splicing of cellular pre-mRNAs. Most spliceosomal snRNPs contain a common set of Sm proteins SNRPB, SNRPD1, SNRPD2, SNRPD3, SNRPE, SNRPF and SNRPG that assemble in a heptameric protein ring on the Sm site of the small nuclear RNA to form the core snRNP. In the cytosol, the Sm proteins SNRPD1, SNRPD2, SNRPE, SNRPF and SNRPG are trapped in an inactive 6S pICln-Sm complex by the chaperone CLNS1A that controls the assembly of the core snRNP. Dissociation by the SMN complex of CLNS1A from the trapped Sm proteins and their transfer to an SMN-Sm complex triggers the assembly of core snRNPs and their transport to the nucleus.2 Publications

GO - Biological processi

  • mRNA processing Source: ProtInc
  • nuclear import Source: Reactome
  • RNA splicing Source: UniProtKB
  • RNA splicing, via transesterification reactions Source: UniProtKB
  • spliceosomal complex assembly Source: ProtInc
  • spliceosomal snRNP assembly Source: UniProtKB
Complete GO annotation...

Keywords - Biological processi

mRNA processing, mRNA splicing

Enzyme and pathway databases

ReactomeiR-HSA-191859. snRNP Assembly.

Names & Taxonomyi

Protein namesi
Recommended name:
Gem-associated protein 2
Short name:
Gemin-2
Alternative name(s):
Component of gems 2
Survival of motor neuron protein-interacting protein 1
Short name:
SMN-interacting protein 1
Gene namesi
Name:GEMIN2
Synonyms:SIP1
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
Proteomesi
  • UP000005640 Componenti: Chromosome 14

Organism-specific databases

HGNCiHGNC:10884. GEMIN2.

Subcellular locationi

  • Nucleusgem
  • Cytoplasm

  • Note: Localized in subnuclear structures next to coiled bodies, called gems, which are highly enriched in spliceosomal snRNPs. Also found in the cytoplasm.

GO - Cellular componenti

  • cytoplasm Source: HPA
  • cytosol Source: UniProtKB
  • Gemini of coiled bodies Source: UniProtKB-SubCell
  • nucleolus Source: HPA
  • nucleoplasm Source: Reactome
  • nucleus Source: HPA
  • SMN complex Source: UniProtKB
  • SMN-Sm protein complex Source: UniProtKB
  • spliceosomal complex Source: InterPro
Complete GO annotation...

Keywords - Cellular componenti

Cytoplasm, Nucleus

Pathology & Biotechi

Organism-specific databases

PharmGKBiPA35784.

Polymorphism and mutation databases

BioMutaiGEMIN2.

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Chaini1 – 280280Gem-associated protein 2PRO_0000087455Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei81 – 811PhosphoserineCombined sources
Modified residuei166 – 1661PhosphoserineCombined sources

Keywords - PTMi

Phosphoprotein

Proteomic databases

EPDiO14893.
MaxQBiO14893.
PaxDbiO14893.
PRIDEiO14893.

PTM databases

iPTMnetiO14893.
PhosphoSiteiO14893.

Expressioni

Gene expression databases

BgeeiO14893.
CleanExiHS_SIP1.
ExpressionAtlasiO14893. baseline and differential.
GenevisibleiO14893. HS.

Organism-specific databases

HPAiCAB015426.
HPA046570.
HPA057114.

Interactioni

Subunit structurei

Part of the core SMN complex that contains SMN1, GEMIN2/SIP1, DDX20/GEMIN3, GEMIN4, GEMIN5, GEMIN6, GEMIN7, GEMIN8 and STRAP/UNRIP. Part of the SMN-Sm complex that contains SMN1, GEMIN2/SIP1, DDX20/GEMIN3, GEMIN4, GEMIN5, GEMIN6, GEMIN7, GEMIN8, STRAP/UNRIP and the Sm proteins SNRPB, SNRPD1, SNRPD2, SNRPD3, SNRPE, SNRPF and SNRPG. Interacts directly with GEMIN5.3 Publications

Binary interactionsi

WithEntry#Exp.IntActNotes
SMN2Q1663713EBI-443648,EBI-395421

Protein-protein interaction databases

BioGridi114059. 60 interactions.
DIPiDIP-32605N.
IntActiO14893. 29 interactions.
MINTiMINT-151615.
STRINGi9606.ENSP00000308533.

Structurei

Secondary structure

1
280
Legend: HelixTurnBeta strand
Show more details
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Helixi48 – 6215Combined sources
Beta strandi65 – 684Combined sources
Helixi100 – 12122Combined sources
Helixi141 – 1488Combined sources
Helixi152 – 1554Combined sources
Beta strandi158 – 1603Combined sources
Turni161 – 1644Combined sources
Turni172 – 1743Combined sources
Helixi180 – 1834Combined sources
Helixi188 – 20013Combined sources
Helixi201 – 2033Combined sources
Helixi209 – 22113Combined sources
Helixi228 – 24417Combined sources
Helixi245 – 2473Combined sources
Helixi255 – 26814Combined sources
Turni273 – 2753Combined sources

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
2LEHNMR-A95-280[»]
3S6NX-ray2.5021-280[»]
ProteinModelPortaliO14893.
SMRiO14893. Positions 22-280.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Compositional bias

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Compositional biasi101 – 1066Poly-Gln

Sequence similaritiesi

Belongs to the gemin-2 family.Curated

Phylogenomic databases

eggNOGiENOG410IJ8K. Eukaryota.
ENOG410YM8D. LUCA.
GeneTreeiENSGT00390000013814.
HOVERGENiHBG051719.
InParanoidiO14893.
KOiK13130.
OMAiQRAAPYN.
OrthoDBiEOG7XH6RF.
PhylomeDBiO14893.
TreeFamiTF105864.

Family and domain databases

InterProiIPR017364. GEMIN2.
[Graphical view]
PIRSFiPIRSF038038. SMN_Gemin2. 1 hit.

Sequences (4)i

Sequence statusi: Complete.

This entry describes 4 isoformsi produced by alternative splicing. AlignAdd to basket

Isoform 1 (identifier: O14893-1) [UniParc]FASTAAdd to basket

Also known as: SIP1-alpha

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
MRRAELAGLK TMAWVPAESA VEELMPRLLP VEPCDLTEGF DPSVPPRTPQ
60 70 80 90 100
EYLRRVQIEA AQCPDVVVAQ IDPKKLKRKQ SVNISLSGCQ PAPEGYSPTL
110 120 130 140 150
QWQQQQVAQF STVRQNVNKH RSHWKSQQLD SNVTMPKSED EEGWKKFCLG
160 170 180 190 200
EKLCADGAVG PATNESPGID YVQIGFPPLL SIVSRMNQAT VTSVLEYLSN
210 220 230 240 250
WFGERDFTPE LGRWLYALLA CLEKPLLPEA HSLIRQLARR CSEVRLLVDS
260 270 280
KDDERVPALN LLICLVSRYF DQRDLADEPS
Length:280
Mass (Da):31,585
Last modified:January 1, 1998 - v1
Checksum:i3232F410EA98EB81
GO
Isoform 2 (identifier: O14893-2) [UniParc]FASTAAdd to basket

Also known as: SIP1-beta

The sequence of this isoform differs from the canonical sequence as follows:
     173-187: Missing.

Show »
Length:265
Mass (Da):29,931
Checksum:iFE91C496F663B825
GO
Isoform 3 (identifier: O14893-3) [UniParc]FASTAAdd to basket

Also known as: SIP1-gamma

The sequence of this isoform differs from the canonical sequence as follows:
     249-250: DS → VF
     251-280: Missing.

Show »
Length:250
Mass (Da):28,155
Checksum:i4DD0F378D5B7C837
GO
Isoform 4 (identifier: O14893-4) [UniParc]FASTAAdd to basket

Also known as: SIP1-delta

The sequence of this isoform differs from the canonical sequence as follows:
     31-44: VEPCDLTEGFDPSV → DRSSSMSRCCGSSN
     45-280: Missing.

Show »
Length:44
Mass (Da):4,826
Checksum:iA7BE4D4FDDE48411
GO

Sequence cautioni

The sequence CAC16117.2 differs from that shown. Reason: Erroneous initiation. Translation N-terminally extended.Curated

Alternative sequence

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Alternative sequencei31 – 4414VEPCD…FDPSV → DRSSSMSRCCGSSN in isoform 4. 1 PublicationVSP_013543Add
BLAST
Alternative sequencei45 – 280236Missing in isoform 4. 1 PublicationVSP_013544Add
BLAST
Alternative sequencei173 – 18715Missing in isoform 2. 1 PublicationVSP_013545Add
BLAST
Alternative sequencei249 – 2502DS → VF in isoform 3. 1 PublicationVSP_013546
Alternative sequencei251 – 28030Missing in isoform 3. 1 PublicationVSP_013547Add
BLAST

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AF027150 mRNA. Translation: AAB82297.1.
AB037701 mRNA. Translation: BAB03508.1.
AB037702 mRNA. Translation: BAB03509.1.
AB037703 mRNA. Translation: BAB03510.1.
AJ250932
, AJ250933, AJ250934, AJ250935, AJ250936, AJ250937, AJ250938, AJ250939 Genomic DNA. Translation: CAC16117.2. Different initiation.
AK313947 mRNA. Translation: BAG36665.1.
BC104968 mRNA. Translation: AAI04969.1.
CCDSiCCDS32068.1. [O14893-2]
CCDS41946.1. [O14893-3]
CCDS9669.1. [O14893-1]
RefSeqiNP_001009182.1. NM_001009182.1. [O14893-2]
NP_001009183.1. NM_001009183.1. [O14893-3]
NP_003607.1. NM_003616.2. [O14893-1]
UniGeneiHs.652307.

Genome annotation databases

EnsembliENST00000250379; ENSP00000250379; ENSG00000092208. [O14893-2]
ENST00000308317; ENSP00000308533; ENSG00000092208. [O14893-1]
ENST00000396249; ENSP00000379548; ENSG00000092208. [O14893-3]
ENST00000412033; ENSP00000416827; ENSG00000092208. [O14893-4]
GeneIDi8487.
KEGGihsa:8487.
UCSCiuc001wuq.4. human. [O14893-1]

Keywords - Coding sequence diversityi

Alternative splicing

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AF027150 mRNA. Translation: AAB82297.1.
AB037701 mRNA. Translation: BAB03508.1.
AB037702 mRNA. Translation: BAB03509.1.
AB037703 mRNA. Translation: BAB03510.1.
AJ250932
, AJ250933, AJ250934, AJ250935, AJ250936, AJ250937, AJ250938, AJ250939 Genomic DNA. Translation: CAC16117.2. Different initiation.
AK313947 mRNA. Translation: BAG36665.1.
BC104968 mRNA. Translation: AAI04969.1.
CCDSiCCDS32068.1. [O14893-2]
CCDS41946.1. [O14893-3]
CCDS9669.1. [O14893-1]
RefSeqiNP_001009182.1. NM_001009182.1. [O14893-2]
NP_001009183.1. NM_001009183.1. [O14893-3]
NP_003607.1. NM_003616.2. [O14893-1]
UniGeneiHs.652307.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
2LEHNMR-A95-280[»]
3S6NX-ray2.5021-280[»]
ProteinModelPortaliO14893.
SMRiO14893. Positions 22-280.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi114059. 60 interactions.
DIPiDIP-32605N.
IntActiO14893. 29 interactions.
MINTiMINT-151615.
STRINGi9606.ENSP00000308533.

PTM databases

iPTMnetiO14893.
PhosphoSiteiO14893.

Polymorphism and mutation databases

BioMutaiGEMIN2.

Proteomic databases

EPDiO14893.
MaxQBiO14893.
PaxDbiO14893.
PRIDEiO14893.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000250379; ENSP00000250379; ENSG00000092208. [O14893-2]
ENST00000308317; ENSP00000308533; ENSG00000092208. [O14893-1]
ENST00000396249; ENSP00000379548; ENSG00000092208. [O14893-3]
ENST00000412033; ENSP00000416827; ENSG00000092208. [O14893-4]
GeneIDi8487.
KEGGihsa:8487.
UCSCiuc001wuq.4. human. [O14893-1]

Organism-specific databases

CTDi8487.
GeneCardsiGEMIN2.
GeneReviewsiGEMIN2.
HGNCiHGNC:10884. GEMIN2.
HPAiCAB015426.
HPA046570.
HPA057114.
MIMi602595. gene.
neXtProtiNX_O14893.
PharmGKBiPA35784.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiENOG410IJ8K. Eukaryota.
ENOG410YM8D. LUCA.
GeneTreeiENSGT00390000013814.
HOVERGENiHBG051719.
InParanoidiO14893.
KOiK13130.
OMAiQRAAPYN.
OrthoDBiEOG7XH6RF.
PhylomeDBiO14893.
TreeFamiTF105864.

Enzyme and pathway databases

ReactomeiR-HSA-191859. snRNP Assembly.

Miscellaneous databases

ChiTaRSiGEMIN2. human.
GenomeRNAii8487.
PROiO14893.
SOURCEiSearch...

Gene expression databases

BgeeiO14893.
CleanExiHS_SIP1.
ExpressionAtlasiO14893. baseline and differential.
GenevisibleiO14893. HS.

Family and domain databases

InterProiIPR017364. GEMIN2.
[Graphical view]
PIRSFiPIRSF038038. SMN_Gemin2. 1 hit.
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "The spinal muscular atrophy disease gene product, SMN, and its associated protein SIP1 are in a complex with spliceosomal snRNP proteins."
    Liu Q., Fischer U., Wang F., Dreyfuss G.
    Cell 90:1013-1021(1997) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 1), FUNCTION, SUBUNIT, SUBCELLULAR LOCATION.
    Tissue: Mammary cancer.
  2. "Increased expression level of the splicing variant of SIP1 in motor neuron diseases."
    Aerbajinai W., Ishihara T., Arahata K., Tsukahara T.
    Int. J. Biochem. Cell Biol. 34:699-707(2002) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORMS 2; 3 AND 4).
    Tissue: Spinal cord.
  3. "An essential SMN interacting protein (SIP1) is not involved in the phenotypic variability of spinal muscular atrophy (SMA)."
    Helmken C., Wetter A., Rudnik-Schoeneborn S., Liehr T., Zerres K., Wirth B.
    Eur. J. Hum. Genet. 8:493-499(2000) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA].
  4. "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 1).
    Tissue: Skeletal muscle.
  5. "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: Brain.
  6. "Gemin5, a novel WD repeat protein component of the SMN complex that binds Sm proteins."
    Gubitz A.K., Mourelatos Z., Abel L., Rappsilber J., Mann M., Dreyfuss G.
    J. Biol. Chem. 277:5631-5636(2002) [PubMed] [Europe PMC] [Abstract]
    Cited for: INTERACTION WITH GEMIN5 AND THE SMN COMPLEX, SUBCELLULAR LOCATION.
  7. "An assembly chaperone collaborates with the SMN complex to generate spliceosomal SnRNPs."
    Chari A., Golas M.M., Klingenhager M., Neuenkirchen N., Sander B., Englbrecht C., Sickmann A., Stark H., Fischer U.
    Cell 135:497-509(2008) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION IN SNRNP BIOGENESIS, IDENTIFICATION IN SMN-SM COMPLEX.
  8. "Kinase-selective enrichment enables quantitative phosphoproteomics of the kinome across the cell cycle."
    Daub H., Olsen J.V., Bairlein M., Gnad F., Oppermann F.S., Korner R., Greff Z., Keri G., Stemmann O., Mann M.
    Mol. Cell 31:438-448(2008) [PubMed] [Europe PMC] [Abstract]
    Cited for: PHOSPHORYLATION [LARGE SCALE ANALYSIS] AT SER-166, IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
    Tissue: Cervix carcinoma.
  9. Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
    Tissue: Cervix carcinoma.
  10. "Lys-N and trypsin cover complementary parts of the phosphoproteome in a refined SCX-based approach."
    Gauci S., Helbig A.O., Slijper M., Krijgsveld J., Heck A.J., Mohammed S.
    Anal. Chem. 81:4493-4501(2009) [PubMed] [Europe PMC] [Abstract]
    Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
  11. Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
  12. "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: PHOSPHORYLATION [LARGE SCALE ANALYSIS] AT SER-81, IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
    Tissue: Liver.

Entry informationi

Entry nameiGEMI2_HUMAN
AccessioniPrimary (citable) accession number: O14893
Secondary accession number(s): B2R9W8
, Q2M3B3, Q9H4F5, Q9NS77, Q9NS78, Q9NS79
Entry historyi
Integrated into UniProtKB/Swiss-Prot: July 15, 1999
Last sequence update: January 1, 1998
Last modified: June 8, 2016
This is version 149 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

Caution

It is uncertain whether Met-1 or Met-12 is the initiator.Curated

Keywords - Technical termi

3D-structure, Complete proteome, Reference proteome

Documents

  1. Human chromosome 14
    Human chromosome 14: 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. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  4. 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.