Skip Header

You are using a version of browser that may not display all the features of this website. Please consider upgrading your browser.
Protein

Histone acetyltransferase type B catalytic subunit

Gene

HAT1

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

Functioni

Acetylates soluble but not nucleosomal histone H4 at 'Lys-5' (H4K5ac) and 'Lys-12' (H4K12ac) and, to a lesser extent, acetylates histone H2A at 'Lys-5' (H2AK5ac). Has intrinsic substrate specificity that modifies lysine in recognition sequence GXGKXG. May be involved in nucleosome assembly during DNA replication and repair as part of the histone H3.1 and H3.3 complexes. May play a role in DNA repair in response to free radical damage.4 Publications

Catalytic activityi

Acetyl-CoA + [histone] = CoA + acetyl-[histone].3 Publications

Kineticsi

kcat is 4.14 (sec-1) for acetyl-CoA.1 Publication

  1. KM=6.68 µM for acetyl-CoA1 Publication

Sites

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sitei199 – 1991Interaction with histone H4 N-terminus1 Publication
Active sitei276 – 2761Proton donor/acceptor1 Publication

GO - Molecular functioni

  1. H4 histone acetyltransferase activity Source: UniProtKB
  2. histone acetyltransferase activity Source: ProtInc

GO - Biological processi

  1. chromatin organization Source: Reactome
  2. chromatin silencing at telomere Source: InterPro
  3. DNA packaging Source: ProtInc
  4. DNA replication-dependent nucleosome assembly Source: UniProtKB
  5. DNA replication-independent nucleosome assembly Source: UniProtKB
  6. histone H4 acetylation Source: UniProtKB
  7. internal protein amino acid acetylation Source: ProtInc
  8. response to nutrient Source: Ensembl
Complete GO annotation...

Keywords - Molecular functioni

Acyltransferase, Transferase

Enzyme and pathway databases

ReactomeiREACT_172610. HATs acetylate histones.

Names & Taxonomyi

Protein namesi
Recommended name:
Histone acetyltransferase type B catalytic subunit (EC:2.3.1.483 Publications)
Alternative name(s):
Histone acetyltransferase 1
Gene namesi
Name:HAT1
Synonyms:KAT1
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
ProteomesiUP000005640: Chromosome 2

Organism-specific databases

HGNCiHGNC:4821. HAT1.

Subcellular locationi

Isoform B : Cytoplasm. Nucleus. Nucleus matrix. Nucleusnucleoplasm
Note: Localization is predominantly nuclear in normal cells. Treatment with hydrogen peroxide or ionizing radiation enhances nuclear localization through redistribution of existing protein.

GO - Cellular componenti

  1. cytoplasm Source: UniProtKB-SubCell
  2. intracellular membrane-bounded organelle Source: HPA
  3. nuclear chromatin Source: UniProtKB
  4. nuclear matrix Source: UniProtKB-SubCell
  5. nucleoplasm Source: HPA
  6. nucleus Source: ProtInc
  7. protein complex Source: UniProtKB
Complete GO annotation...

Keywords - Cellular componenti

Cytoplasm, Nucleus

Pathology & Biotechi

Mutagenesis

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Mutagenesisi62 – 621D → A: Strongly reduces HAT activity. 1 Publication
Mutagenesisi64 – 641E → A: Strongly reduces HAT activity. 1 Publication
Mutagenesisi187 – 1871E → Q: Strongly reduces HAT activity. 1 Publication
Mutagenesisi199 – 1991W → A: Strongly reduces HAT activity. 1 Publication
Mutagenesisi276 – 2761E → Q: Strongly reduces HAT activity. 1 Publication
Mutagenesisi277 – 2771D → N: Strongly reduces HAT activity. 1 Publication

Organism-specific databases

PharmGKBiPA29197.

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Initiator methioninei1 – 11Removed2 Publications
Chaini2 – 419418Histone acetyltransferase type B catalytic subunitPRO_0000083902Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei2 – 21N-acetylalanine2 Publications
Modified residuei9 – 91N6-acetyllysineBy similarity
Modified residuei15 – 151N6-acetyllysineBy similarity

Keywords - PTMi

Acetylation

Proteomic databases

MaxQBiO14929.
PaxDbiO14929.
PeptideAtlasiO14929.
PRIDEiO14929.

PTM databases

PhosphoSiteiO14929.

Expressioni

Developmental stagei

Highly expressed in mitotic cells (at protein level).1 Publication

Inductioni

Up-regulated by estrogen.1 Publication

Gene expression databases

BgeeiO14929.
CleanExiHS_HAT1.
ExpressionAtlasiO14929. baseline and differential.
GenevestigatoriO14929.

Organism-specific databases

HPAiHPA036788.

Interactioni

Subunit structurei

Catalytic subunit of the type B histone acetyltransferase (HAT) complex, composed of RBBP7 and HAT1. Interacts with histones H4 and H2A. The interaction is dependent of the ability of RBBP7 to bind to the N-terminus of histones. Component of the histone H3.1 and H3.3 complexes.3 Publications

Binary interactionsi

WithEntry#Exp.IntActNotes
HIST2H4BP628054EBI-2339359,EBI-302023
vprP125203EBI-2339359,EBI-6164519From a different organism.

Protein-protein interaction databases

BioGridi114092. 32 interactions.
DIPiDIP-52811N.
IntActiO14929. 12 interactions.
MINTiMINT-2795393.
STRINGi9606.ENSP00000264108.

Structurei

Secondary structure

1
419
Legend: HelixTurnBeta strand
Show more details
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Beta strandi26 – 283Combined sources
Helixi29 – 324Combined sources
Beta strandi33 – 408Combined sources
Helixi41 – 444Combined sources
Helixi47 – 493Combined sources
Helixi57 – 604Combined sources
Turni61 – 644Combined sources
Beta strandi65 – 717Combined sources
Beta strandi73 – 797Combined sources
Turni80 – 823Combined sources
Beta strandi85 – 906Combined sources
Beta strandi92 – 943Combined sources
Turni97 – 993Combined sources
Beta strandi100 – 1023Combined sources
Helixi107 – 1126Combined sources
Helixi123 – 1319Combined sources
Helixi132 – 1354Combined sources
Beta strandi140 – 1489Combined sources
Beta strandi157 – 1648Combined sources
Helixi171 – 18515Combined sources
Beta strandi199 – 21012Combined sources
Beta strandi213 – 22917Combined sources
Turni230 – 2323Combined sources
Beta strandi233 – 24311Combined sources
Helixi245 – 2473Combined sources
Helixi252 – 26514Combined sources
Beta strandi273 – 2775Combined sources
Helixi280 – 29415Combined sources
Helixi298 – 3003Combined sources
Helixi302 – 3054Combined sources
Helixi311 – 32111Combined sources
Helixi325 – 33915Combined sources

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
2P0WX-ray1.90A/B20-341[»]
ProteinModelPortaliO14929.
SMRiO14929. Positions 23-341.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiO14929.

Family & Domainsi

Region

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Regioni62 – 643Interaction with histone H4 N-terminus1 Publication
Regioni225 – 2273Interaction with histone H4 N-terminusCurated
Regioni241 – 2433Acetyl-CoA binding1 Publication
Regioni248 – 2547Acetyl-CoA binding1 Publication

Sequence similaritiesi

Belongs to the HAT1 family.Curated

Phylogenomic databases

eggNOGiNOG326277.
HOGENOMiHOG000231943.
HOVERGENiHBG005945.
InParanoidiO14929.
KOiK11303.
OMAiEVAFGYK.
PhylomeDBiO14929.
TreeFamiTF314995.

Family and domain databases

Gene3Di3.40.630.30. 1 hit.
3.90.360.10. 1 hit.
InterProiIPR016181. Acyl_CoA_acyltransferase.
IPR019467. Hat1_N.
IPR017380. Hist_AcTrfase_B-typ_cat-su.
[Graphical view]
PANTHERiPTHR12046. PTHR12046. 1 hit.
PfamiPF10394. Hat1_N. 1 hit.
[Graphical view]
PIRSFiPIRSF038084. HAT-B_cat. 1 hit.
SUPFAMiSSF55729. SSF55729. 1 hit.

Sequences (2)i

Sequence statusi: Complete.

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

This entry describes 2 isoformsi produced by alternative splicing. Align

Isoform A (identifier: O14929-1) [UniParc]FASTAAdd to Basket

Also known as: a, Nuclear

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
MAGFGAMEKF LVEYKSAVEK KLAEYKCNTN TAIELKLVRF PEDLENDIRT
60 70 80 90 100
FFPEYTHQLF GDDETAFGYK GLKILLYYIA GSLSTMFRVE YASKVDENFD
110 120 130 140 150
CVEADDVEGK IRQIIPPGFC TNTNDFLSLL EKEVDFKPFG TLLHTYSVLS
160 170 180 190 200
PTGGENFTFQ IYKADMTCRG FREYHERLQT FLMWFIETAS FIDVDDERWH
210 220 230 240 250
YFLVFEKYNK DGATLFATVG YMTVYNYYVY PDKTRPRVSQ MLILTPFQGQ
260 270 280 290 300
GHGAQLLETV HRYYTEFPTV LDITAEDPSK SYVKLRDFVL VKLCQDLPCF
310 320 330 340 350
SREKLMQGFN EDMAIEAQQK FKINKQHARR VYEILRLLVT DMSDAEQYRS
360 370 380 390 400
YRLDIKRRLI SPYKKKQRDL AKMRKCLRPE ELTNQMNQIE ISMQHEQLEE
410
SFQELVEDYR RVIERLAQE
Length:419
Mass (Da):49,513
Last modified:January 1, 1998 - v1
Checksum:i509DF06E0E4E2647
GO
Isoform B (identifier: O14929-2) [UniParc]FASTAAdd to Basket

Also known as: b

The sequence of this isoform differs from the canonical sequence as follows:
     1-85: Missing.

Show »
Length:334
Mass (Da):39,786
Checksum:i40E4B9925CD5DF81
GO

Sequence cautioni

The sequence AAH18682.1 differs from that shown. Reason: Erroneous initiation. Translation N-terminally extended.Curated

Natural variant

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Natural varianti317 – 3171A → P in a colorectal cancer sample; somatic mutation. 1 Publication
VAR_035997

Alternative sequence

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Alternative sequencei1 – 8585Missing in isoform B. 1 PublicationVSP_041129Add
BLAST

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AF030424 mRNA. Translation: AAC02425.1.
AC015976 Genomic DNA. Translation: AAY14731.1.
AC114745 Genomic DNA. Translation: AAX93247.1.
CH471058 Genomic DNA. Translation: EAX11195.1.
BC018682 mRNA. Translation: AAH18682.1. Different initiation.
BC045673 mRNA. No translation available.
BC063003 mRNA. Translation: AAH63003.1.
CCDSiCCDS2245.1. [O14929-1]
RefSeqiNP_003633.1. NM_003642.3. [O14929-1]
UniGeneiHs.632532.

Genome annotation databases

EnsembliENST00000264108; ENSP00000264108; ENSG00000128708.
GeneIDi8520.
KEGGihsa:8520.
UCSCiuc002uhi.3. human. [O14929-1]
uc010fqi.2. human. [O14929-2]

Keywords - Coding sequence diversityi

Alternative splicing, Polymorphism

Cross-referencesi

Web resourcesi

Wikipedia

Histone acetyltransferase entry

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AF030424 mRNA. Translation: AAC02425.1.
AC015976 Genomic DNA. Translation: AAY14731.1.
AC114745 Genomic DNA. Translation: AAX93247.1.
CH471058 Genomic DNA. Translation: EAX11195.1.
BC018682 mRNA. Translation: AAH18682.1. Different initiation.
BC045673 mRNA. No translation available.
BC063003 mRNA. Translation: AAH63003.1.
CCDSiCCDS2245.1. [O14929-1]
RefSeqiNP_003633.1. NM_003642.3. [O14929-1]
UniGeneiHs.632532.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
2P0WX-ray1.90A/B20-341[»]
ProteinModelPortaliO14929.
SMRiO14929. Positions 23-341.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi114092. 32 interactions.
DIPiDIP-52811N.
IntActiO14929. 12 interactions.
MINTiMINT-2795393.
STRINGi9606.ENSP00000264108.

PTM databases

PhosphoSiteiO14929.

Proteomic databases

MaxQBiO14929.
PaxDbiO14929.
PeptideAtlasiO14929.
PRIDEiO14929.

Protocols and materials databases

DNASUi8520.
Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000264108; ENSP00000264108; ENSG00000128708.
GeneIDi8520.
KEGGihsa:8520.
UCSCiuc002uhi.3. human. [O14929-1]
uc010fqi.2. human. [O14929-2]

Organism-specific databases

CTDi8520.
GeneCardsiGC02P172779.
HGNCiHGNC:4821. HAT1.
HPAiHPA036788.
MIMi603053. gene.
neXtProtiNX_O14929.
PharmGKBiPA29197.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiNOG326277.
HOGENOMiHOG000231943.
HOVERGENiHBG005945.
InParanoidiO14929.
KOiK11303.
OMAiEVAFGYK.
PhylomeDBiO14929.
TreeFamiTF314995.

Enzyme and pathway databases

ReactomeiREACT_172610. HATs acetylate histones.

Miscellaneous databases

ChiTaRSiHAT1. human.
EvolutionaryTraceiO14929.
GeneWikiiHAT1.
GenomeRNAii8520.
NextBioi31898.
PROiO14929.
SOURCEiSearch...

Gene expression databases

BgeeiO14929.
CleanExiHS_HAT1.
ExpressionAtlasiO14929. baseline and differential.
GenevestigatoriO14929.

Family and domain databases

Gene3Di3.40.630.30. 1 hit.
3.90.360.10. 1 hit.
InterProiIPR016181. Acyl_CoA_acyltransferase.
IPR019467. Hat1_N.
IPR017380. Hist_AcTrfase_B-typ_cat-su.
[Graphical view]
PANTHERiPTHR12046. PTHR12046. 1 hit.
PfamiPF10394. Hat1_N. 1 hit.
[Graphical view]
PIRSFiPIRSF038084. HAT-B_cat. 1 hit.
SUPFAMiSSF55729. SSF55729. 1 hit.
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "Nucleosomal DNA regulates the core-histone-binding subunit of the human Hat1 acetyltransferase."
    Verreault A., Kaufman P.D., Kobayashi R., Stillman B.
    Curr. Biol. 8:96-108(1998) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM A), FUNCTION, ENZYME ACTIVITY, SUBUNIT, SUBCELLULAR LOCATION.
    Tissue: Teratocarcinoma.
  2. "Generation and annotation of the DNA sequences of human chromosomes 2 and 4."
    Hillier L.W., Graves T.A., Fulton R.S., Fulton L.A., Pepin K.H., Minx P., Wagner-McPherson C., Layman D., Wylie K., Sekhon M., Becker M.C., Fewell G.A., Delehaunty K.D., Miner T.L., Nash W.E., Kremitzki C., Oddy L., Du H.
    , Sun H., Bradshaw-Cordum H., Ali J., Carter J., Cordes M., Harris A., Isak A., van Brunt A., Nguyen C., Du F., Courtney L., Kalicki J., Ozersky P., Abbott S., Armstrong J., Belter E.A., Caruso L., Cedroni M., Cotton M., Davidson T., Desai A., Elliott G., Erb T., Fronick C., Gaige T., Haakenson W., Haglund K., Holmes A., Harkins R., Kim K., Kruchowski S.S., Strong C.M., Grewal N., Goyea E., Hou S., Levy A., Martinka S., Mead K., McLellan M.D., Meyer R., Randall-Maher J., Tomlinson C., Dauphin-Kohlberg S., Kozlowicz-Reilly A., Shah N., Swearengen-Shahid S., Snider J., Strong J.T., Thompson J., Yoakum M., Leonard S., Pearman C., Trani L., Radionenko M., Waligorski J.E., Wang C., Rock S.M., Tin-Wollam A.-M., Maupin R., Latreille P., Wendl M.C., Yang S.-P., Pohl C., Wallis J.W., Spieth J., Bieri T.A., Berkowicz N., Nelson J.O., Osborne J., Ding L., Meyer R., Sabo A., Shotland Y., Sinha P., Wohldmann P.E., Cook L.L., Hickenbotham M.T., Eldred J., Williams D., Jones T.A., She X., Ciccarelli F.D., Izaurralde E., Taylor J., Schmutz J., Myers R.M., Cox D.R., Huang X., McPherson J.D., Mardis E.R., Clifton S.W., Warren W.C., Chinwalla A.T., Eddy S.R., Marra M.A., Ovcharenko I., Furey T.S., Miller W., Eichler E.E., Bork P., Suyama M., Torrents D., Waterston R.H., Wilson R.K.
    Nature 434:724-731(2005) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
  3. Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
  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] (ISOFORM B), NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA] OF 2-419 (ISOFORM A).
    Tissue: Brain, Lung and Testis.
  5. "Effects of acetylation of histone H4 at lysines 8 and 16 on activity of the Hat1 histone acetyltransferase."
    Makowski A.M., Dutnall R.N., Annunziato A.T.
    J. Biol. Chem. 276:43499-43502(2001) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, CATALYTIC ACTIVITY.
  6. "Quantitative real-time RT-PCR analysis of eight novel estrogen-regulated genes in breast cancer."
    Sorbello V., Fuso L., Sfiligoi C., Scafoglio C., Ponzone R., Biglia N., Weisz A., Sismondi P., De Bortoli M.
    Int. J. Biol. Markers 18:123-129(2003) [PubMed] [Europe PMC] [Abstract]
    Cited for: INDUCTION BY ESTROGEN.
  7. "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: ACETYLATION [LARGE SCALE ANALYSIS] AT ALA-2, IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS], CLEAVAGE OF INITIATOR METHIONINE [LARGE SCALE ANALYSIS].
  8. "Irradiation with heavy-ion particles changes the cellular distribution of human histone acetyltransferase HAT1."
    Lebel E.A., Boukamp P., Tafrov S.T.
    Mol. Cell. Biochem. 339:271-284(2010) [PubMed] [Europe PMC] [Abstract]
    Cited for: SUBCELLULAR LOCATION, DEVELOPMENTAL STAGE.
  9. Cited for: FUNCTION, SUBUNIT, SUBCELLULAR LOCATION.
  10. Cited for: IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
  11. "Comparative large-scale characterisation of plant vs. mammal proteins reveals similar and idiosyncratic N-alpha acetylation features."
    Bienvenut W.V., Sumpton D., Martinez A., Lilla S., Espagne C., Meinnel T., Giglione C.
    Mol. Cell. Proteomics 11:M111.015131-M111.015131(2012) [PubMed] [Europe PMC] [Abstract]
    Cited for: ACETYLATION [LARGE SCALE ANALYSIS] AT ALA-2, IDENTIFICATION BY MASS SPECTROMETRY [LARGE SCALE ANALYSIS].
  12. "Structural basis for substrate specificity and catalysis of human histone acetyltransferase 1."
    Wu H., Moshkina N., Min J., Zeng H., Joshua J., Zhou M.M., Plotnikov A.N.
    Proc. Natl. Acad. Sci. U.S.A. 109:8925-8930(2012) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (1.90 ANGSTROMS) OF 20-341 IN COMPLEX WITH ACETYL-COA AND HISTONE H4 PEPTIDE, CATALYTIC ACTIVITY, FUNCTION, BIOPHYSICOCHEMICAL PROPERTIES, MUTAGENESIS OF ASP-62; GLU-64; GLU-187; TRP-199; GLU-276 AND ASP-277, ACTIVE SITE, INTERACTION WITH HISTONE H4.
  13. Cited for: VARIANT [LARGE SCALE ANALYSIS] PRO-317.

Entry informationi

Entry nameiHAT1_HUMAN
AccessioniPrimary (citable) accession number: O14929
Secondary accession number(s): Q49A44
, Q53QF0, Q53SU4, Q6P594, Q8WWB9
Entry historyi
Integrated into UniProtKB/Swiss-Prot: July 15, 1998
Last sequence update: January 1, 1998
Last modified: February 4, 2015
This is version 129 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

Keywords - Technical termi

3D-structure, Complete proteome, Reference proteome

Documents

  1. Human chromosome 2
    Human chromosome 2: 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. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  6. 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.