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Protein

Retina-specific copper amine oxidase

Gene

AOC2

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

Functioni

Has a monoamine oxidase activity with substrate specificity for 2-phenylethylamine and tryptamine. May play a role in adipogenesis. May be a critical modulator of signal transmission in retina.2 Publications

Catalytic activityi

RCH2NH2 + H2O + O2 = RCHO + NH3 + H2O2.

Cofactori

Protein has several cofactor binding sites:
  • Cu cationBy similarityNote: Binds 1 copper ion per subunit.By similarity
  • Ca2+By similarityNote: Binds 2 calcium ions per subunit.By similarity
  • L-topaquinoneBy similarityNote: Contains 1 topaquinone per subunit.By similarity

Kineticsi

  1. KM=0.056 mM for tryptamine1 Publication
  2. KM=0.077 mM for 2-phenylethylamine1 Publication
  3. KM=0.167 mM for benzylamine1 Publication
  4. KM=0.178 mM for p-tyramine1 Publication
  5. KM=1.7 mM for methylamine1 Publication

    Sites

    Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
    Active sitei380 – 3801Proton acceptorBy similarity
    Active sitei465 – 4651Schiff-base intermediate with substrate; via topaquinoneBy similarity
    Metal bindingi516 – 5161CopperBy similarity
    Metal bindingi518 – 5181CopperBy similarity
    Metal bindingi525 – 5251Calcium 1By similarity
    Metal bindingi526 – 5261Calcium 1; via carbonyl oxygenBy similarity
    Metal bindingi527 – 5271Calcium 1By similarity
    Metal bindingi568 – 5681Calcium 2By similarity
    Metal bindingi634 – 6341Calcium 2By similarity
    Metal bindingi659 – 6591Calcium 2; via carbonyl oxygenBy similarity
    Metal bindingi661 – 6611Calcium 2By similarity
    Metal bindingi663 – 6631Calcium 2By similarity
    Metal bindingi669 – 6691Calcium 1By similarity
    Metal bindingi670 – 6701Calcium 1; via carbonyl oxygenBy similarity
    Metal bindingi680 – 6801CopperBy similarity

    GO - Molecular functioni

    GO - Biological processi

    • amine metabolic process Source: InterPro
    • catecholamine metabolic process Source: UniProtKB-KW
    • visual perception Source: ProtInc
    Complete GO annotation...

    Keywords - Molecular functioni

    Oxidoreductase

    Keywords - Biological processi

    Catecholamine metabolism

    Keywords - Ligandi

    Calcium, Copper, Metal-binding

    Enzyme and pathway databases

    BRENDAi1.4.3.21. 2681.
    SABIO-RKO75106.

    Names & Taxonomyi

    Protein namesi
    Recommended name:
    Retina-specific copper amine oxidase (EC:1.4.3.21)
    Short name:
    RAO
    Alternative name(s):
    Amine oxidase [copper-containing]
    Semicarbazide-sensitive amine oxidase
    Short name:
    SSAO
    Gene namesi
    Name:AOC2
    OrganismiHomo sapiens (Human)
    Taxonomic identifieri9606 [NCBI]
    Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
    ProteomesiUP000005640 Componenti: Chromosome 17

    Organism-specific databases

    HGNCiHGNC:549. AOC2.

    Subcellular locationi

    Isoform 1 :
    Isoform 2 :
    • Cytoplasm

    • Note: Either not translocated to the plasma membrane or below detection level.

    GO - Cellular componenti

    Complete GO annotation...

    Keywords - Cellular componenti

    Cell membrane, Cytoplasm, Membrane

    Pathology & Biotechi

    Organism-specific databases

    PharmGKBiPA24839.

    Polymorphism and mutation databases

    BioMutaiAOC2.

    PTM / Processingi

    Molecule processing

    Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
    Signal peptidei1 – 3232Sequence AnalysisAdd
    BLAST
    Chaini33 – 756724Retina-specific copper amine oxidasePRO_0000035671Add
    BLAST

    Amino acid modifications

    Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
    Glycosylationi133 – 1331N-linked (GlcNAc...)Sequence Analysis
    Glycosylationi198 – 1981N-linked (GlcNAc...)Sequence Analysis
    Glycosylationi226 – 2261N-linked (GlcNAc...)Sequence Analysis
    Modified residuei465 – 46512',4',5'-topaquinoneBy similarity
    Glycosylationi588 – 5881N-linked (GlcNAc...)Sequence Analysis
    Glycosylationi662 – 6621N-linked (GlcNAc...)Sequence Analysis

    Post-translational modificationi

    Topaquinone (TPQ) is generated by copper-dependent autoxidation of a specific tyrosyl residue.

    Keywords - PTMi

    Glycoprotein, TPQ

    Proteomic databases

    PaxDbiO75106.
    PRIDEiO75106.

    PTM databases

    PhosphoSiteiO75106.

    Expressioni

    Tissue specificityi

    Expressed in many tissues with much higher expression in retina. Isoform 1 and isoform 2 are expressed in adipose tissue, whereas isoform 1 only seems to be present in thymus, and isoform 2 only in testis.3 Publications

    Inductioni

    Up-regulated during in vitro adipocyte differentiation.1 Publication

    Gene expression databases

    BgeeiO75106.
    CleanExiHS_AOC2.
    GenevestigatoriO75106.

    Organism-specific databases

    HPAiHPA057779.

    Interactioni

    Subunit structurei

    Forms a heterodimer with AOC3, in vitro.1 Publication

    Protein-protein interaction databases

    BioGridi106811. 2 interactions.
    STRINGi9606.ENSP00000253799.

    Structurei

    3D structure databases

    ProteinModelPortaliO75106.
    SMRiO75106. Positions 51-756.
    ModBaseiSearch...
    MobiDBiSearch...

    Family & Domainsi

    Sequence similaritiesi

    Belongs to the copper/topaquinone oxidase family.Curated

    Keywords - Domaini

    Signal

    Phylogenomic databases

    eggNOGiCOG3733.
    GeneTreeiENSGT00510000046461.
    HOGENOMiHOG000233919.
    HOVERGENiHBG004164.
    InParanoidiO75106.
    KOiK00276.
    OMAiVDIHILV.
    OrthoDBiEOG7353W8.
    PhylomeDBiO75106.
    TreeFamiTF314750.

    Family and domain databases

    Gene3Di2.70.98.20. 1 hit.
    3.10.450.40. 2 hits.
    InterProiIPR000269. Cu_amine_oxidase.
    IPR015798. Cu_amine_oxidase_C.
    IPR016182. Cu_amine_oxidase_N-reg.
    IPR015800. Cu_amine_oxidase_N2.
    IPR015801. Cu_amine_oxidase_N2/3.
    IPR015802. Cu_amine_oxidase_N3.
    [Graphical view]
    PANTHERiPTHR10638. PTHR10638. 1 hit.
    PfamiPF01179. Cu_amine_oxid. 1 hit.
    PF02727. Cu_amine_oxidN2. 1 hit.
    PF02728. Cu_amine_oxidN3. 1 hit.
    [Graphical view]
    PRINTSiPR00766. CUDAOXIDASE.
    SUPFAMiSSF49998. SSF49998. 1 hit.
    SSF54416. SSF54416. 2 hits.
    PROSITEiPS01164. COPPER_AMINE_OXID_1. 1 hit.
    PS01165. COPPER_AMINE_OXID_2. 1 hit.
    [Graphical view]

    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. AlignAdd to basket

    Note: Additional isoforms seem to exist.

    Isoform 1 (identifier: O75106-1) [UniParc]FASTAAdd to basket

    Also known as: Long

    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
    MHLKIVLAFL ALSLITIFAL AYVLLTSPGG SSQPPHCPSV SHRAQPWPHP
    60 70 80 90 100
    GQSQLFADLS REELTAVMRF LTQRLGPGLV DAAQAQPSDN CIFSVELQLP
    110 120 130 140 150
    PKAAALAHLD RGSPPPAREA LAIVLFGGQP QPNVSELVVG PLPHPSYMRD
    160 170 180 190 200
    VTVERHGGPL PYHRRPVLRA EFTQMWRHLK EVELPKAPIF LSSTFNYNGS
    210 220 230 240 250
    TLAAVHATPR GLRSGDRATW MALYHNISGV GLFLHPVGLE LLLDHRALDP
    260 270 280 290 300
    AHWTVQQVFY LGHYYADLGQ LEREFKSGRL EVVRVPLPPP NGASSLRSRN
    310 320 330 340 350
    SPGPLPPLQF SPQGSQYSVQ GNLVVSSLWS FTFGHGVFSG LRIFDVRFQG
    360 370 380 390 400
    ERIAYEVSVQ ECVSIYGADS PKTMLTRYLD SSFGLGRNSR GLVRGVDCPY
    410 420 430 440 450
    QATMVDIHIL VGKGAVQLLP GAVCVFEEAQ GLPLRRHHNY LQNHFYGGLA
    460 470 480 490 500
    SSALVVRSVS SVGNYDYIWD FVLYPNGALE GRVHATGYIN TAFLKGGEEG
    510 520 530 540 550
    LLFGNRVGER VLGTVHTHAF HFKLDLDVAG LKNWVVAEDV VFKPVAAPWN
    560 570 580 590 600
    PEHWLQRPQL TRQVLGKEDL TAFSLGSPLP RYLYLASNQT NAWGHQRGYR
    610 620 630 640 650
    IQIHSPLGIH IPLESDMERA LSWGRYQLVV TQRKEEESQS SSIYHQNDIW
    660 670 680 690 700
    TPTVTFADFI NNETLLGEDL VAWVTASFLH IPHAEDIPNT VTLGNRVGFL
    710 720 730 740 750
    LRPYNFFDED PSIFSPGSVY FEKGQDAGLC SINPVACLPD LAACVPDLPP

    FSYHGF
    Length:756
    Mass (Da):83,673
    Last modified:January 24, 2006 - v2
    Checksum:i10263D8D56D3BD25
    GO
    Isoform 2 (identifier: O75106-2) [UniParc]FASTAAdd to basket

    Also known as: Short

    The sequence of this isoform differs from the canonical sequence as follows:
         599-625: Missing.

    Show »
    Length:729
    Mass (Da):80,516
    Checksum:i5F28CCC8EE353415
    GO

    Experimental Info

    Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
    Sequence conflicti181 – 1811E → D (PubMed:9119395).Curated
    Sequence conflicti181 – 1811E → D (PubMed:9722954).Curated
    Sequence conflicti215 – 2184GDRA → RERT (PubMed:9119395).Curated
    Sequence conflicti215 – 2184GDRA → RERT (PubMed:9722954).Curated
    Sequence conflicti221 – 2222MA → IG (PubMed:9119395).Curated
    Sequence conflicti610 – 6101H → Q (PubMed:9119395).Curated
    Sequence conflicti610 – 6101H → Q (PubMed:9722954).Curated

    Natural variant

    Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
    Natural varianti5 – 51I → V.1 Publication
    Corresponds to variant rs34230945 [ dbSNP | Ensembl ].
    VAR_025022
    Natural varianti22 – 221Y → C.1 Publication
    Corresponds to variant rs34435306 [ dbSNP | Ensembl ].
    VAR_025023
    Natural varianti141 – 1411P → L.1 Publication
    Corresponds to variant rs35833794 [ dbSNP | Ensembl ].
    VAR_025024
    Natural varianti273 – 2731R → Q.1 Publication
    Corresponds to variant rs35508987 [ dbSNP | Ensembl ].
    VAR_025025
    Natural varianti427 – 4271E → D.1 Publication
    Corresponds to variant rs34351794 [ dbSNP | Ensembl ].
    VAR_025026

    Alternative sequence

    Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
    Alternative sequencei599 – 62527Missing in isoform 2. 1 PublicationVSP_006549Add
    BLAST

    Sequence databases

    Select the link destinations:
    EMBLi
    GenBanki
    DDBJi
    Links Updated
    D88213 mRNA. Translation: BAA19001.1.
    AB012943 Genomic DNA. Translation: BAA32590.1.
    AB012943 Genomic DNA. Translation: BAA32589.1.
    AF081363 mRNA. Translation: AAD39345.1.
    DQ060035 Genomic DNA. Translation: AAY43129.1.
    AC016889 Genomic DNA. No translation available.
    CH471152 Genomic DNA. Translation: EAW60895.1.
    BC142641 mRNA. Translation: AAI42642.1.
    CCDSiCCDS11443.1. [O75106-1]
    CCDS45690.1. [O75106-2]
    RefSeqiNP_001149.2. NM_001158.3. [O75106-2]
    NP_033720.2. NM_009590.2. [O75106-1]
    UniGeneiHs.143102.

    Genome annotation databases

    EnsembliENST00000253799; ENSP00000253799; ENSG00000131480. [O75106-1]
    ENST00000452774; ENSP00000406134; ENSG00000131480. [O75106-2]
    GeneIDi314.
    KEGGihsa:314.
    UCSCiuc002ibt.3. human. [O75106-2]
    uc002ibu.3. human. [O75106-1]

    Keywords - Coding sequence diversityi

    Alternative splicing, Polymorphism

    Cross-referencesi

    Web resourcesi

    NIEHS-SNPs

    Sequence databases

    Select the link destinations:
    EMBLi
    GenBanki
    DDBJi
    Links Updated
    D88213 mRNA. Translation: BAA19001.1.
    AB012943 Genomic DNA. Translation: BAA32590.1.
    AB012943 Genomic DNA. Translation: BAA32589.1.
    AF081363 mRNA. Translation: AAD39345.1.
    DQ060035 Genomic DNA. Translation: AAY43129.1.
    AC016889 Genomic DNA. No translation available.
    CH471152 Genomic DNA. Translation: EAW60895.1.
    BC142641 mRNA. Translation: AAI42642.1.
    CCDSiCCDS11443.1. [O75106-1]
    CCDS45690.1. [O75106-2]
    RefSeqiNP_001149.2. NM_001158.3. [O75106-2]
    NP_033720.2. NM_009590.2. [O75106-1]
    UniGeneiHs.143102.

    3D structure databases

    ProteinModelPortaliO75106.
    SMRiO75106. Positions 51-756.
    ModBaseiSearch...
    MobiDBiSearch...

    Protein-protein interaction databases

    BioGridi106811. 2 interactions.
    STRINGi9606.ENSP00000253799.

    Chemistry

    BindingDBiO75106.
    ChEMBLiCHEMBL4112.

    PTM databases

    PhosphoSiteiO75106.

    Polymorphism and mutation databases

    BioMutaiAOC2.

    Proteomic databases

    PaxDbiO75106.
    PRIDEiO75106.

    Protocols and materials databases

    Structural Biology KnowledgebaseSearch...

    Genome annotation databases

    EnsembliENST00000253799; ENSP00000253799; ENSG00000131480. [O75106-1]
    ENST00000452774; ENSP00000406134; ENSG00000131480. [O75106-2]
    GeneIDi314.
    KEGGihsa:314.
    UCSCiuc002ibt.3. human. [O75106-2]
    uc002ibu.3. human. [O75106-1]

    Organism-specific databases

    CTDi314.
    GeneCardsiGC17P040996.
    HGNCiHGNC:549. AOC2.
    HPAiHPA057779.
    MIMi602268. gene.
    neXtProtiNX_O75106.
    PharmGKBiPA24839.
    GenAtlasiSearch...

    Phylogenomic databases

    eggNOGiCOG3733.
    GeneTreeiENSGT00510000046461.
    HOGENOMiHOG000233919.
    HOVERGENiHBG004164.
    InParanoidiO75106.
    KOiK00276.
    OMAiVDIHILV.
    OrthoDBiEOG7353W8.
    PhylomeDBiO75106.
    TreeFamiTF314750.

    Enzyme and pathway databases

    BRENDAi1.4.3.21. 2681.
    SABIO-RKO75106.

    Miscellaneous databases

    GenomeRNAii314.
    NextBioi1277.
    PROiO75106.
    SOURCEiSearch...

    Gene expression databases

    BgeeiO75106.
    CleanExiHS_AOC2.
    GenevestigatoriO75106.

    Family and domain databases

    Gene3Di2.70.98.20. 1 hit.
    3.10.450.40. 2 hits.
    InterProiIPR000269. Cu_amine_oxidase.
    IPR015798. Cu_amine_oxidase_C.
    IPR016182. Cu_amine_oxidase_N-reg.
    IPR015800. Cu_amine_oxidase_N2.
    IPR015801. Cu_amine_oxidase_N2/3.
    IPR015802. Cu_amine_oxidase_N3.
    [Graphical view]
    PANTHERiPTHR10638. PTHR10638. 1 hit.
    PfamiPF01179. Cu_amine_oxid. 1 hit.
    PF02727. Cu_amine_oxidN2. 1 hit.
    PF02728. Cu_amine_oxidN3. 1 hit.
    [Graphical view]
    PRINTSiPR00766. CUDAOXIDASE.
    SUPFAMiSSF49998. SSF49998. 1 hit.
    SSF54416. SSF54416. 2 hits.
    PROSITEiPS01164. COPPER_AMINE_OXID_1. 1 hit.
    PS01165. COPPER_AMINE_OXID_2. 1 hit.
    [Graphical view]
    ProtoNetiSearch...

    Publicationsi

    « Hide 'large scale' publications
    1. "Human retina-specific amine oxidase (RAO): cDNA cloning, tissue expression, and chromosomal mapping."
      Imamura Y., Kubota R., Wang Y., Asakawa S., Kudoh J., Mashima Y., Oguchi Y., Shimizu N.
      Genomics 40:277-283(1997) [PubMed] [Europe PMC] [Abstract]
      Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 2).
      Tissue: Retina.
    2. "Human retina-specific amine oxidase: genomic structure of the gene (AOC2), alternatively spliced variant, and mRNA expression in retina."
      Imamura Y., Noda S., Mashima Y., Kudoh J., Oguchi Y., Shimizu N.
      Genomics 51:293-298(1998) [PubMed] [Europe PMC] [Abstract]
      Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA], ALTERNATIVE SPLICING.
    3. "Human copper-containing amine oxidases."
      Zhang X., McIntire W.S.
      Submitted (JUL-1998) to the EMBL/GenBank/DDBJ databases
      Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 1).
      Tissue: Retina.
    4. NIEHS SNPs program
      Submitted (MAY-2005) to the EMBL/GenBank/DDBJ databases
      Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA], VARIANTS VAL-5; CYS-22; LEU-141; GLN-273 AND ASP-427.
    5. "DNA sequence of human chromosome 17 and analysis of rearrangement in the human lineage."
      Zody M.C., Garber M., Adams D.J., Sharpe T., Harrow J., Lupski J.R., Nicholson C., Searle S.M., Wilming L., Young S.K., Abouelleil A., Allen N.R., Bi W., Bloom T., Borowsky M.L., Bugalter B.E., Butler J., Chang J.L.
      , Chen C.-K., Cook A., Corum B., Cuomo C.A., de Jong P.J., DeCaprio D., Dewar K., FitzGerald M., Gilbert J., Gibson R., Gnerre S., Goldstein S., Grafham D.V., Grocock R., Hafez N., Hagopian D.S., Hart E., Norman C.H., Humphray S., Jaffe D.B., Jones M., Kamal M., Khodiyar V.K., LaButti K., Laird G., Lehoczky J., Liu X., Lokyitsang T., Loveland J., Lui A., Macdonald P., Major J.E., Matthews L., Mauceli E., McCarroll S.A., Mihalev A.H., Mudge J., Nguyen C., Nicol R., O'Leary S.B., Osoegawa K., Schwartz D.C., Shaw-Smith C., Stankiewicz P., Steward C., Swarbreck D., Venkataraman V., Whittaker C.A., Yang X., Zimmer A.R., Bradley A., Hubbard T., Birren B.W., Rogers J., Lander E.S., Nusbaum C.
      Nature 440:1045-1049(2006) [PubMed] [Europe PMC] [Abstract]
      Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    6. Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    7. "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).
    8. "High expression of semicarbazide-sensitive amine oxidase genes AOC2 and AOC3, but not the diamine oxidase gene AOC1 in human adipocytes."
      Heniquez A., Meissonnier G., Visentin V., Prevot D., Carpene C.
      Inflamm. Res. 52:S74-S75(2003) [PubMed] [Europe PMC] [Abstract]
      Cited for: TISSUE SPECIFICITY.
    9. "Adipogenesis-related increase of semicarbazide-sensitive amine oxidase and monoamine oxidase in human adipocytes."
      Bour S., Daviaud D., Gres S., Lefort C., Prevot D., Zorzano A., Wabitsch M., Saulnier-Blache J.-S., Valet P., Carpene C.
      Biochimie 89:916-925(2007) [PubMed] [Europe PMC] [Abstract]
      Cited for: FUNCTION, TISSUE SPECIFICITY, INDUCTION.
    10. "The unique substrate specificity of human AOC2, a semicarbazide-sensitive amine oxidase."
      Kaitaniemi S., Elovaara H., Groen K., Kidron H., Liukkonen J., Salminen T., Salmi M., Jalkanen S., Elima K.
      Cell. Mol. Life Sci. 66:2743-2757(2009) [PubMed] [Europe PMC] [Abstract]
      Cited for: FUNCTION, SUBCELLULAR LOCATION, SUBUNIT, TISSUE SPECIFICITY, BIOPHYSICOCHEMICAL PROPERTIES.

    Entry informationi

    Entry nameiAOC2_HUMAN
    AccessioniPrimary (citable) accession number: O75106
    Secondary accession number(s): A5PKW2
    , O00120, O75105, Q4TTW5, Q9UNY0
    Entry historyi
    Integrated into UniProtKB/Swiss-Prot: July 15, 1999
    Last sequence update: January 24, 2006
    Last modified: April 29, 2015
    This is version 132 of the entry and version 2 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, Reference proteome

    Documents

    1. Human chromosome 17
      Human chromosome 17: 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.