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Protein

4-aminobutyrate aminotransferase, mitochondrial

Gene

ABAT

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

Functioni

Catalyzes the conversion of gamma-aminobutyrate and L-beta-aminoisobutyrate to succinate semialdehyde and methylmalonate semialdehyde, respectively. Can also convert delta-aminovalerate and beta-alanine.

Catalytic activityi

4-aminobutanoate + 2-oxoglutarate = succinate semialdehyde + L-glutamate.
(S)-3-amino-2-methylpropanoate + 2-oxoglutarate = 2-methyl-3-oxopropanoate + L-glutamate.

Cofactori

pyridoxal 5'-phosphateBy similarity, [2Fe-2S] clusterBy similarityNote: Binds 1 [2Fe-2S] cluster per homodimer.By similarity

Sites

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Metal bindingi163 – 1631Iron-sulfur (2Fe-2S); shared with dimeric partnerBy similarity
Metal bindingi166 – 1661Iron-sulfur (2Fe-2S); shared with dimeric partnerBy similarity
Binding sitei220 – 2201SubstrateBy similarity
Binding sitei381 – 3811Pyridoxal phosphate; shared with dimeric partnerBy similarity

GO - Molecular functioni

  1. (S)-3-amino-2-methylpropionate transaminase activity Source: UniProtKB-EC
  2. 4-aminobutyrate transaminase activity Source: Reactome
  3. iron-sulfur cluster binding Source: UniProtKB-KW
  4. metal ion binding Source: UniProtKB-KW
  5. protein homodimerization activity Source: UniProtKB
  6. pyridoxal phosphate binding Source: UniProtKB
  7. succinate-semialdehyde dehydrogenase binding Source: UniProtKB

GO - Biological processi

  1. behavioral response to cocaine Source: UniProtKB
  2. copulation Source: Ensembl
  3. gamma-aminobutyric acid catabolic process Source: UniProtKB
  4. locomotory behavior Source: Ensembl
  5. negative regulation of blood pressure Source: Ensembl
  6. neurotransmitter catabolic process Source: UniProtKB
  7. neurotransmitter secretion Source: Reactome
  8. response to drug Source: Ensembl
  9. response to ethanol Source: Ensembl
  10. response to hypoxia Source: Ensembl
  11. response to iron ion Source: Ensembl
  12. response to nicotine Source: Ensembl
  13. synaptic transmission Source: Reactome
Complete GO annotation...

Keywords - Molecular functioni

Aminotransferase, Transferase

Keywords - Biological processi

Neurotransmitter degradation

Keywords - Ligandi

Iron, Iron-sulfur, Metal-binding, Pyridoxal phosphate

Enzyme and pathway databases

BioCyciMetaCyc:HS02477-MONOMER.
ReactomeiREACT_23964. Degradation of GABA.
SABIO-RKP80404.

Names & Taxonomyi

Protein namesi
Recommended name:
4-aminobutyrate aminotransferase, mitochondrial (EC:2.6.1.19)
Alternative name(s):
(S)-3-amino-2-methylpropionate transaminase (EC:2.6.1.22)
GABA aminotransferase
Short name:
GABA-AT
Gamma-amino-N-butyrate transaminase
Short name:
GABA transaminase
Short name:
GABA-T
L-AIBAT
Gene namesi
Name:ABAT
Synonyms:GABAT
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
ProteomesiUP000005640 Componenti: Chromosome 16

Organism-specific databases

HGNCiHGNC:23. ABAT.

Subcellular locationi

GO - Cellular componenti

  1. 4-aminobutyrate transaminase complex Source: UniProtKB
  2. extracellular vesicular exosome Source: UniProtKB
  3. mitochondrial matrix Source: Reactome
  4. mitochondrion Source: UniProtKB
  5. neuron projection Source: Ensembl
Complete GO annotation...

Keywords - Cellular componenti

Mitochondrion

Pathology & Biotechi

Involvement in diseasei

GABA transaminase deficiency (GABATD)1 Publication

The disease is caused by mutations affecting the gene represented in this entry.

Disease descriptionAn enzymatic deficiency resulting in psychomotor retardation, hypotonia, hyperreflexia, lethargy, refractory seizures, and EEG abnormalities.

See also OMIM:613163
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Natural varianti220 – 2201R → K in GABATD; 25% reduction in activity. 1 Publication
VAR_008883

Mutagenesis

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Mutagenesisi321 – 3211C → M, S, A, G or K: Loss of activity. 1 Publication

Keywords - Diseasei

Disease mutation

Organism-specific databases

MIMi613163. phenotype.
Orphaneti2066. Gamma-aminobutyric acid transaminase deficiency.
PharmGKBiPA24372.

Chemistry

DrugBankiDB00160. L-Alanine.
DB00780. Phenelzine.
DB00119. Pyruvic acid.
DB00313. Valproic Acid.
DB01080. Vigabatrin.

Polymorphism and mutation databases

BioMutaiABAT.
DMDMi48429239.

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Transit peptidei1 – 2828MitochondrionAdd
BLAST
Chaini29 – 5004724-aminobutyrate aminotransferase, mitochondrialPRO_0000001249Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei231 – 2311N6-succinyllysineBy similarity
Modified residuei252 – 2521N6-acetyllysine; alternateBy similarity
Modified residuei252 – 2521N6-succinyllysine; alternateBy similarity
Modified residuei279 – 2791N6-acetyllysineBy similarity
Modified residuei318 – 3181N6-acetyllysineBy similarity
Disulfide bondi321 – 321Interchain
Modified residuei357 – 3571N6-(pyridoxal phosphate)lysineBy similarity
Modified residuei413 – 4131N6-acetyllysine; alternateBy similarity
Modified residuei413 – 4131N6-succinyllysine; alternateBy similarity
Modified residuei452 – 4521N6-acetyllysineBy similarity
Modified residuei470 – 4701N6-acetyllysineBy similarity

Keywords - PTMi

Acetylation, Disulfide bond

Proteomic databases

MaxQBiP80404.
PaxDbiP80404.
PeptideAtlasiP80404.
PRIDEiP80404.

PTM databases

PhosphoSiteiP80404.

Expressioni

Tissue specificityi

Liver > pancreas > brain > kidney > heart > placenta.

Gene expression databases

BgeeiP80404.
CleanExiHS_ABAT.
ExpressionAtlasiP80404. baseline and differential.
GenevestigatoriP80404.

Organism-specific databases

HPAiHPA041528.
HPA041690.

Interactioni

Subunit structurei

Homodimer; disulfide-linked.1 Publication

Protein-protein interaction databases

BioGridi106536. 3 interactions.
IntActiP80404. 1 interaction.
STRINGi9606.ENSP00000268251.

Structurei

3D structure databases

ProteinModelPortaliP80404.
SMRiP80404. Positions 39-499.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Region

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Regioni164 – 1652Pyridoxal phosphate bindingBy similarity

Sequence similaritiesi

Keywords - Domaini

Transit peptide

Phylogenomic databases

eggNOGiCOG0160.
HOVERGENiHBG000634.
InParanoidiP80404.
KOiK13524.
OrthoDBiEOG7ZPNJW.
PhylomeDBiP80404.
TreeFamiTF105021.

Family and domain databases

Gene3Di3.40.640.10. 1 hit.
3.90.1150.10. 2 hits.
InterProiIPR004631. 4NH2But_aminotransferase_euk.
IPR005814. Aminotrans_3.
IPR015424. PyrdxlP-dep_Trfase.
IPR015421. PyrdxlP-dep_Trfase_major_sub1.
IPR015422. PyrdxlP-dep_Trfase_major_sub2.
[Graphical view]
PANTHERiPTHR11986. PTHR11986. 1 hit.
PTHR11986:SF6. PTHR11986:SF6. 1 hit.
PfamiPF00202. Aminotran_3. 1 hit.
[Graphical view]
PIRSFiPIRSF000521. Transaminase_4ab_Lys_Orn. 1 hit.
SUPFAMiSSF53383. SSF53383. 1 hit.
TIGRFAMsiTIGR00699. GABAtrns_euk. 1 hit.
PROSITEiPS00600. AA_TRANSFER_CLASS_3. 1 hit.
[Graphical view]

Sequencei

Sequence statusi: Complete.

Sequence processingi: The displayed sequence is further processed into a mature form.

P80404-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MASMLLAQRL ACSFQHSYRL LVPGSRHISQ AAAKVDVEFD YDGPLMKTEV
60 70 80 90 100
PGPRSQELMK QLNIIQNAEA VHFFCNYEES RGNYLVDVDG NRMLDLYSQI
110 120 130 140 150
SSVPIGYSHP ALLKLIQQPQ NASMFVNRPA LGILPPENFV EKLRQSLLSV
160 170 180 190 200
APKGMSQLIT MACGSCSNEN ALKTIFMWYR SKERGQRGFS QEELETCMIN
210 220 230 240 250
QAPGCPDYSI LSFMGAFHGR TMGCLATTHS KAIHKIDIPS FDWPIAPFPR
260 270 280 290 300
LKYPLEEFVK ENQQEEARCL EEVEDLIVKY RKKKKTVAGI IVEPIQSEGG
310 320 330 340 350
DNHASDDFFR KLRDIARKHG CAFLVDEVQT GGGCTGKFWA HEHWGLDDPA
360 370 380 390 400
DVMTFSKKMM TGGFFHKEEF RPNAPYRIFN TWLGDPSKNL LLAEVINIIK
410 420 430 440 450
REDLLNNAAH AGKALLTGLL DLQARYPQFI SRVRGRGTFC SFDTPDDSIR
460 470 480 490 500
NKLILIARNK GVVLGGCGDK SIRFRPTLVF RDHHAHLFLN IFSDILADFK
Length:500
Mass (Da):56,439
Last modified:June 7, 2004 - v3
Checksum:iF990B0B6B77BD3F5
GO

Experimental Info

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sequence conflicti17 – 171S → T in AAA74449 (PubMed:7721088).Curated
Sequence conflicti109 – 1091H → D in AAA74449 (PubMed:7721088).Curated
Sequence conflicti113 – 1131L → V in AAA74449 (PubMed:7721088).Curated
Sequence conflicti132 – 1321G → E in AAA74449 (PubMed:7721088).Curated
Sequence conflicti155 – 17117MSQLI…SNENA → CPSSSPWPACPAPMKTT in AAB38510 (Ref. 2) CuratedAdd
BLAST
Sequence conflicti191 – 1911Q → K in AAA74449 (PubMed:7721088).Curated
Sequence conflicti204 – 2041G → W in AAA74449 (PubMed:7721088).Curated
Sequence conflicti216 – 2161A → S in AAA74449 (PubMed:7721088).Curated
Sequence conflicti247 – 2471P → T in AAB38510 (Ref. 2) Curated
Sequence conflicti268 – 2681R → G in AAA74449 (PubMed:7721088).Curated
Sequence conflicti320 – 3201G → C in AAA74449 (PubMed:7721088).Curated
Sequence conflicti366 – 3661H → L in AAA74449 (PubMed:7721088).Curated

Natural variant

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Natural varianti56 – 561Q → R.1 Publication
Corresponds to variant rs1731017 [ dbSNP | Ensembl ].
VAR_018979
Natural varianti220 – 2201R → K in GABATD; 25% reduction in activity. 1 Publication
VAR_008883

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
L32961 mRNA. Translation: AAA74449.1.
U80226 mRNA. Translation: AAB38510.1.
AK290501 mRNA. Translation: BAF83190.1.
BC015628 mRNA. Translation: AAH15628.1.
BC031413 mRNA. Translation: AAH31413.1.
S75578 mRNA. Translation: AAD14176.1.
CCDSiCCDS10534.1.
PIRiJC4022.
S67470.
RefSeqiNP_000654.2. NM_000663.4.
NP_001120920.1. NM_001127448.1.
NP_065737.2. NM_020686.5.
UniGeneiHs.336768.

Genome annotation databases

EnsembliENST00000268251; ENSP00000268251; ENSG00000183044.
ENST00000396600; ENSP00000379845; ENSG00000183044.
ENST00000425191; ENSP00000411916; ENSG00000183044.
GeneIDi18.
KEGGihsa:18.
UCSCiuc002czc.4. human.

Polymorphism and mutation databases

BioMutaiABAT.

Keywords - Coding sequence diversityi

Polymorphism

Cross-referencesi

Web resourcesi

SHMPD

The Singapore human mutation and polymorphism database

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
L32961 mRNA. Translation: AAA74449.1.
U80226 mRNA. Translation: AAB38510.1.
AK290501 mRNA. Translation: BAF83190.1.
BC015628 mRNA. Translation: AAH15628.1.
BC031413 mRNA. Translation: AAH31413.1.
S75578 mRNA. Translation: AAD14176.1.
CCDSiCCDS10534.1.
PIRiJC4022.
S67470.
RefSeqiNP_000654.2. NM_000663.4.
NP_001120920.1. NM_001127448.1.
NP_065737.2. NM_020686.5.
UniGeneiHs.336768.

3D structure databases

ProteinModelPortaliP80404.
SMRiP80404. Positions 39-499.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi106536. 3 interactions.
IntActiP80404. 1 interaction.
STRINGi9606.ENSP00000268251.

Chemistry

BindingDBiP80404.
ChEMBLiCHEMBL2044.
DrugBankiDB00160. L-Alanine.
DB00780. Phenelzine.
DB00119. Pyruvic acid.
DB00313. Valproic Acid.
DB01080. Vigabatrin.
GuidetoPHARMACOLOGYi2464.

PTM databases

PhosphoSiteiP80404.

Polymorphism and mutation databases

BioMutaiABAT.
DMDMi48429239.

Proteomic databases

MaxQBiP80404.
PaxDbiP80404.
PeptideAtlasiP80404.
PRIDEiP80404.

Protocols and materials databases

DNASUi18.
Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000268251; ENSP00000268251; ENSG00000183044.
ENST00000396600; ENSP00000379845; ENSG00000183044.
ENST00000425191; ENSP00000411916; ENSG00000183044.
GeneIDi18.
KEGGihsa:18.
UCSCiuc002czc.4. human.

Organism-specific databases

CTDi18.
GeneCardsiGC16P008768.
HGNCiHGNC:23. ABAT.
HPAiHPA041528.
HPA041690.
MIMi137150. gene.
613163. phenotype.
neXtProtiNX_P80404.
Orphaneti2066. Gamma-aminobutyric acid transaminase deficiency.
PharmGKBiPA24372.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiCOG0160.
HOVERGENiHBG000634.
InParanoidiP80404.
KOiK13524.
OrthoDBiEOG7ZPNJW.
PhylomeDBiP80404.
TreeFamiTF105021.

Enzyme and pathway databases

BioCyciMetaCyc:HS02477-MONOMER.
ReactomeiREACT_23964. Degradation of GABA.
SABIO-RKP80404.

Miscellaneous databases

ChiTaRSiABAT. human.
GenomeRNAii18.
NextBioi45.
PROiP80404.
SOURCEiSearch...

Gene expression databases

BgeeiP80404.
CleanExiHS_ABAT.
ExpressionAtlasiP80404. baseline and differential.
GenevestigatoriP80404.

Family and domain databases

Gene3Di3.40.640.10. 1 hit.
3.90.1150.10. 2 hits.
InterProiIPR004631. 4NH2But_aminotransferase_euk.
IPR005814. Aminotrans_3.
IPR015424. PyrdxlP-dep_Trfase.
IPR015421. PyrdxlP-dep_Trfase_major_sub1.
IPR015422. PyrdxlP-dep_Trfase_major_sub2.
[Graphical view]
PANTHERiPTHR11986. PTHR11986. 1 hit.
PTHR11986:SF6. PTHR11986:SF6. 1 hit.
PfamiPF00202. Aminotran_3. 1 hit.
[Graphical view]
PIRSFiPIRSF000521. Transaminase_4ab_Lys_Orn. 1 hit.
SUPFAMiSSF53383. SSF53383. 1 hit.
TIGRFAMsiTIGR00699. GABAtrns_euk. 1 hit.
PROSITEiPS00600. AA_TRANSFER_CLASS_3. 1 hit.
[Graphical view]
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "Screening and sequence determination of a cDNA encoding the human brain 4-aminobutyrate aminotransferase."
    Osei Y.D., Churchich J.E.
    Gene 155:185-187(1995) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA].
    Tissue: Brain.
  2. Medina-Kauwe L.K., Gibson K.M., Nyhan W.L., Tobin A.J.
    Submitted (NOV-1996) to the EMBL/GenBank/DDBJ databases
    Cited for: NUCLEOTIDE SEQUENCE [MRNA].
    Tissue: Pancreatic islet.
  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].
    Tissue: Brain.
  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], VARIANT ARG-56.
    Tissue: Brain and Eye.
  5. "Primary structure and tissue distribution of human 4-aminobutyrate aminotransferase."
    de Biase D., Barra D., Simmaco M., John R.A., Bossa F.
    Eur. J. Biochem. 227:476-480(1995) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] OF 36-485, PARTIAL PROTEIN SEQUENCE.
    Tissue: Liver.
  6. "Cysteine-321 of human brain GABA transaminase is involved in intersubunit cross-linking."
    Yoon C.S., Kim D.W., Jang S.H., Lee B.R., Choi H.S., Choi S.H., Kim S.Y., An J.J., Kwon O.S., Kang T.C., Won M.H., Cho S.W., Lee K.S., Park J., Eum W.S., Choi S.Y.
    Mol. Cells 18:214-219(2004) [PubMed] [Europe PMC] [Abstract]
    Cited for: SUBUNIT, INTERCHAIN DISULFIDE BOND, MUTAGENESIS OF CYS-321.
  7. Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
  8. "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: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
    Tissue: Liver.
  9. Cited for: VARIANT GABATD LYS-220.

Entry informationi

Entry nameiGABT_HUMAN
AccessioniPrimary (citable) accession number: P80404
Secondary accession number(s): A8K386
, Q16260, Q8N5W2, Q96BG2, Q99800
Entry historyi
Integrated into UniProtKB/Swiss-Prot: November 1, 1995
Last sequence update: June 7, 2004
Last modified: April 29, 2015
This is version 148 of the entry and version 3 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, Direct protein sequencing, Reference proteome

Documents

  1. Human chromosome 16
    Human chromosome 16: 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.