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Protein

Hypoxia-inducible factor 1

Gene

hif-1

Organism
Caenorhabditis elegans
Status
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli

Functioni

A transcription factor which is a key regulator in various cellular processes; including environment stress resistance (oxygen levels, hydrogen sulfide and cyanide levels and heat), negative regulation of cell apoptosis in ASJ neurons by inhibition of cep-1 via transcriptional activation of tyr-2, resistance/susceptibility to pathogenic bacteria, lifespan and brood size. Involved in mediating susceptibility to enteropathogenic E.coli (PubMed:16091039). Increased levels of hif-1 activity confer resistance to P.aeruginosa-mediated death but also confer susceptibility to S.aureus infection (PubMed:20865124, PubMed:22792069). Required for aha-1 nuclear localization. Following hypoxic stress, up-regulates serotonin levels through activation of tph-1 expression. Role in life span extension is independent of temperature. Not required for survival in anoxic conditions. Involved in iron homeostasis by repressing transcription of ferritin ftn-1 (PubMed:22396654).15 Publications

GO - Molecular functioni

  • DNA binding Source: UniProtKB-KW
  • RNA polymerase II transcription factor binding Source: WormBase
  • transcription factor activity, sequence-specific DNA binding Source: WormBase

GO - Biological processi

  • apoptotic process Source: UniProtKB-KW
  • cellular response to caloric restriction Source: UniProtKB
  • determination of adult lifespan Source: UniProtKB
  • heat acclimation Source: UniProtKB
  • negative regulation of apoptotic process Source: UniProtKB
  • phosphorelay signal transduction system Source: UniProtKB-KW
  • positive regulation of transcription from RNA polymerase II promoter Source: WormBase
  • response to axon injury Source: WormBase
  • response to hypoxia Source: UniProtKB
  • transcription from RNA polymerase II promoter Source: WormBase
Complete GO annotation...

Keywords - Molecular functioni

Repressor

Keywords - Biological processi

Apoptosis, Stress response, Transcription, Transcription regulation, Two-component regulatory system

Keywords - Ligandi

DNA-binding

Enzyme and pathway databases

ReactomeiR-CEL-1234158. Regulation of gene expression by Hypoxia-inducible Factor.
R-CEL-1234176. Oxygen-dependent proline hydroxylation of Hypoxia-inducible Factor Alpha.

Names & Taxonomyi

Protein namesi
Recommended name:
Hypoxia-inducible factor 12 Publications
Alternative name(s):
Hypoxia-induced factor 11 PublicationImported
Gene namesi
Name:hif-1Imported
ORF Names:F38A6.3
OrganismiCaenorhabditis elegans
Taxonomic identifieri6239 [NCBI]
Taxonomic lineageiEukaryotaMetazoaEcdysozoaNematodaChromadoreaRhabditidaRhabditoideaRhabditidaePeloderinaeCaenorhabditis
Proteomesi
  • UP000001940 Componenti: Chromosome V

Organism-specific databases

WormBaseiF38A6.3a; CE38182; WBGene00001851; hif-1.
F38A6.3b; CE42263; WBGene00001851; hif-1.
F38A6.3c; CE32019; WBGene00001851; hif-1.
F38A6.3d; CE38181; WBGene00001851; hif-1.
F38A6.3e; CE46300; WBGene00001851; hif-1.

Subcellular locationi

  • Nucleus PROSITE-ProRule annotation1 Publication

GO - Cellular componenti

  • nucleus Source: UniProtKB
Complete GO annotation...

Keywords - Cellular componenti

Nucleus

Pathology & Biotechi

Disruption phenotypei

66% do not survive embryogenesis when cultured in hypoxic conditions of 1% oxygen. Able to survive anoxic conditions. Inefficient translocation of aha-1 to the nucleus. Inability to acclimate to heat. Partial resistance to paralysis and killing by enteropathogenic E.coli. Extends lifespan in a temperature dependent manner but not when grown with a restricted diet. At lower temperatures impairs lifespan because of a vulval integrity defect. Unable to survive in even relatively low concentrations of hydrogen sulfide.9 Publications

Mutagenesis

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Mutagenesisi621 – 6211P → G: Loss of egl-9-mediated hydroxylation resulting in the loss of interaction with vhl-1. Normal susceptibility to P.aeruginosa killing. 2 Publications

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Chaini1 – 719719Hypoxia-inducible factor 1PRO_0000416938Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei621 – 62114-hydroxyproline; by egl-91 Publication

Post-translational modificationi

Hydroxylation on Pro-621 by egl-9 during normoxia conditions is required for vhl-1-mediated proteasomal degradation.1 Publication

Keywords - PTMi

Hydroxylation

Proteomic databases

PaxDbiG5EGD2.

Expressioni

Tissue specificityi

Expressed in all somatic cells.2 Publications

Inductioni

By heat acclimation, hypoxia and addition of 50 ppm hydrogen sulfide.3 Publications

Interactioni

Subunit structurei

Binds to aha-1 (PubMed:11427734). Interacts (hydroxylated on Pro-621) with vhl-1; the interaction induces hif-1 degradation (PubMed:11595184).2 Publications

Binary interactionsi

WithEntry#Exp.IntActNotes
aha-1O022193EBI-319821,EBI-2408984

GO - Molecular functioni

  • RNA polymerase II transcription factor binding Source: WormBase

Protein-protein interaction databases

BioGridi45316. 3 interactions.
IntActiG5EGD2. 52 interactions.
STRINGi6239.F38A6.3b.

Structurei

3D structure databases

ProteinModelPortaliG5EGD2.
SMRiG5EGD2. Positions 10-337.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Domains and Repeats

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Domaini11 – 6555bHLHPROSITE-ProRule annotationAdd
BLAST
Domaini86 – 15368PAS 1PROSITE-ProRule annotationAdd
BLAST
Domaini222 – 29271PAS 2PROSITE-ProRule annotationAdd
BLAST
Domaini296 – 34045PACSequence analysisAdd
BLAST

Compositional bias

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Compositional biasi452 – 563112Ser-richSequence analysisAdd
BLAST

Sequence similaritiesi

Contains 1 bHLH (basic helix-loop-helix) domain.PROSITE-ProRule annotation
Contains 1 PAC (PAS-associated C-terminal) domain.Sequence analysis
Contains 2 PAS (PER-ARNT-SIM) domains.PROSITE-ProRule annotation

Keywords - Domaini

Repeat

Phylogenomic databases

eggNOGiKOG3558. Eukaryota.
ENOG410YK57. LUCA.
GeneTreeiENSGT00760000118788.
HOGENOMiHOG000017809.
InParanoidiG5EGD2.
KOiK08268.
OMAiEEPDLSC.
OrthoDBiEOG7JDQX8.

Family and domain databases

InterProiIPR011598. bHLH_dom.
IPR000014. PAS.
IPR013767. PAS_fold.
[Graphical view]
PfamiPF00989. PAS. 1 hit.
[Graphical view]
SMARTiSM00091. PAS. 2 hits.
[Graphical view]
SUPFAMiSSF55785. SSF55785. 2 hits.
TIGRFAMsiTIGR00229. sensory_box. 1 hit.
PROSITEiPS50888. BHLH. 1 hit.
PS50112. PAS. 1 hit.
[Graphical view]

Sequences (5)i

Sequence statusi: Complete.

This entry describes 5 isoformsi produced by alternative splicing. AlignAdd to basket

Isoform a1 Publication (identifier: G5EGD2-1) [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
MEDNRKRNME RRRETSRHAA RDRRSKESDI FDDLKMCVPI VEEGTVTHLD
60 70 80 90 100
RIALLRVAAT ICRLRKTAGN VLENNLDNEI TNEVWTEDTI AECLDGFVMI
110 120 130 140 150
VDSDSSILYV TESVAMYLGL TQTDLTGRAL RDFLHPSDYD EFDKQSKMLH
160 170 180 190 200
KPRGEDTDTT GINMVLRMKT VISPRGRCLN LKSALYKSVS FLVHSKVSTG
210 220 230 240 250
GHVSFMQGIT IPAGQGTTNA NASAMTKYTE SPMGAFTTRH TCDMRITFVS
260 270 280 290 300
DKFNYILKSE LKTLMGTSFY ELVHPADMMI VSKSMKELFA KGHIRTPYYR
310 320 330 340 350
LIAANDTLAW IQTEATTITH TTKGQKGQYV ICVHYVLGIQ GAEESLVVCT
360 370 380 390 400
DSMPAGMQVD IKKEVDDTRD YIGRQPEIVE CVDFTPLIEP EDPFDTVIEP
410 420 430 440 450
VVGGEEPVKQ ADMGARKNSY DDVLQWLFRD QPSSPPPARY RSADRFRTTE
460 470 480 490 500
PSNFGSALAS PDFMDSSSRT SRPKTSYGRR AQSQGSRTTG SSSTSASATL
510 520 530 540 550
PHSANYSPLA EGISQCGLNS PPSIKSGQVV YGDARSMGRS CDPSDSSRRF
560 570 580 590 600
SALSPSDTLN VSSTRGINPV IGSNDVFSTM PFADSIAIAE RIDSSPTLTS
610 620 630 640 650
GEPILCDDLQ WEEPDLSCLA PFVDTYDMMQ MDEGLPPELQ ALYDLPDFTP
660 670 680 690 700
AVPQAPAARP VHIDRSPPAK RMHQSGPSDL DFMYTQHYQP FQQDETYWQG
710
QQQQNEQQPS SYSPFPMLS
Length:719
Mass (Da):79,934
Last modified:December 14, 2011 - v1
Checksum:iE6F5762100E179FE
GO
Isoform b1 Publication (identifier: G5EGD2-2) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     523-523: S → SCS

Note: No experimental confirmation available.Curated
Show »
Length:721
Mass (Da):80,124
Checksum:i2FC85980E721128D
GO
Isoform c1 Publication (identifier: G5EGD2-3) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     1-216: Missing.
     217-226: TTNANASAMT → MSRDSEYLDR

Note: No experimental confirmation available.Curated
Show »
Length:503
Mass (Da):55,860
Checksum:i497E7B6DD02FA597
GO
Isoform d1 Publication (identifier: G5EGD2-4) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     415-719: ARKNSYDDVL...SSYSPFPMLS → IYSVTDEYEQ...LPKGSIRRQH

Note: No experimental confirmation available.Curated
Show »
Length:665
Mass (Da):75,201
Checksum:i7D1D94A215878ACB
GO
Isoform e1 Publication (identifier: G5EGD2-5) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     1-8: Missing.

Note: No experimental confirmation available.Curated
Show »
Length:711
Mass (Da):78,890
Checksum:i78FEAD4A08B0D3BB
GO

Alternative sequence

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Alternative sequencei1 – 216216Missing in isoform c. 1 PublicationVSP_043005Add
BLAST
Alternative sequencei1 – 88Missing in isoform e. 1 PublicationVSP_043006
Alternative sequencei217 – 22610TTNANASAMT → MSRDSEYLDR in isoform c. 1 PublicationVSP_043007
Alternative sequencei415 – 719305ARKNS…FPMLS → IYSVTDEYEQRVYGQISAGN DIEDCDMDSDTESIEDSGLA PEFDVDLAPIYNEKMEVDGE DEDGGEEEHVRTATMTFCNG FFATSQALRRRHATGQRTAS GQPNRRISVPLWPRRTSWIR HLVPPDRRHHTDEEHKVREV EQLDRLPRQHRPHCHTVPTT RHLQRASHNVDLTVPRVSNL DKSCTETLDLWDVAAIRPIR HDAFPPFHHQILSMCRPLEA STQSSEAMMCSPLCLLPILS PLPKGSIRRQH in isoform d. 1 PublicationVSP_043008Add
BLAST
Alternative sequencei523 – 5231S → SCS in isoform b. 1 PublicationVSP_043009

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AF364604 mRNA. Translation: AAK62778.1.
Z92833, AL023842 Genomic DNA. Translation: CAB07380.2.
Z92833, AL023842 Genomic DNA. Translation: CAB07381.2.
AL023842 Genomic DNA. Translation: CAD54167.1.
Z92833, AL023842 Genomic DNA. Translation: CAD54141.2.
Z92833, AL023842 Genomic DNA. Translation: CCD31074.1.
RefSeqiNP_001023891.2. NM_001028720.3. [G5EGD2-2]
NP_001023892.1. NM_001028721.2. [G5EGD2-3]
NP_001023893.1. NM_001028722.3. [G5EGD2-4]
NP_001023894.2. NM_001028723.2. [G5EGD2-5]
NP_508008.4. NM_075607.5. [G5EGD2-1]
UniGeneiCel.17085.

Genome annotation databases

EnsemblMetazoaiF38A6.3a; F38A6.3a; WBGene00001851. [G5EGD2-1]
GeneIDi180359.
KEGGicel:CELE_F38A6.3.

Keywords - Coding sequence diversityi

Alternative splicing

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AF364604 mRNA. Translation: AAK62778.1.
Z92833, AL023842 Genomic DNA. Translation: CAB07380.2.
Z92833, AL023842 Genomic DNA. Translation: CAB07381.2.
AL023842 Genomic DNA. Translation: CAD54167.1.
Z92833, AL023842 Genomic DNA. Translation: CAD54141.2.
Z92833, AL023842 Genomic DNA. Translation: CCD31074.1.
RefSeqiNP_001023891.2. NM_001028720.3. [G5EGD2-2]
NP_001023892.1. NM_001028721.2. [G5EGD2-3]
NP_001023893.1. NM_001028722.3. [G5EGD2-4]
NP_001023894.2. NM_001028723.2. [G5EGD2-5]
NP_508008.4. NM_075607.5. [G5EGD2-1]
UniGeneiCel.17085.

3D structure databases

ProteinModelPortaliG5EGD2.
SMRiG5EGD2. Positions 10-337.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi45316. 3 interactions.
IntActiG5EGD2. 52 interactions.
STRINGi6239.F38A6.3b.

Proteomic databases

PaxDbiG5EGD2.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsemblMetazoaiF38A6.3a; F38A6.3a; WBGene00001851. [G5EGD2-1]
GeneIDi180359.
KEGGicel:CELE_F38A6.3.

Organism-specific databases

CTDi180359.
WormBaseiF38A6.3a; CE38182; WBGene00001851; hif-1.
F38A6.3b; CE42263; WBGene00001851; hif-1.
F38A6.3c; CE32019; WBGene00001851; hif-1.
F38A6.3d; CE38181; WBGene00001851; hif-1.
F38A6.3e; CE46300; WBGene00001851; hif-1.

Phylogenomic databases

eggNOGiKOG3558. Eukaryota.
ENOG410YK57. LUCA.
GeneTreeiENSGT00760000118788.
HOGENOMiHOG000017809.
InParanoidiG5EGD2.
KOiK08268.
OMAiEEPDLSC.
OrthoDBiEOG7JDQX8.

Enzyme and pathway databases

ReactomeiR-CEL-1234158. Regulation of gene expression by Hypoxia-inducible Factor.
R-CEL-1234176. Oxygen-dependent proline hydroxylation of Hypoxia-inducible Factor Alpha.

Miscellaneous databases

NextBioi909024.
PROiG5EGD2.

Family and domain databases

InterProiIPR011598. bHLH_dom.
IPR000014. PAS.
IPR013767. PAS_fold.
[Graphical view]
PfamiPF00989. PAS. 1 hit.
[Graphical view]
SMARTiSM00091. PAS. 2 hits.
[Graphical view]
SUPFAMiSSF55785. SSF55785. 2 hits.
TIGRFAMsiTIGR00229. sensory_box. 1 hit.
PROSITEiPS50888. BHLH. 1 hit.
PS50112. PAS. 1 hit.
[Graphical view]
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "The Caenorhabditis elegans hif-1 gene encodes a bHLH-PAS protein that is required for adaptation to hypoxia."
    Jiang H., Guo R., Powell-Coffman J.A.
    Proc. Natl. Acad. Sci. U.S.A. 98:7916-7921(2001) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM A), FUNCTION, INTERACTION WITH AHA-1, TISSUE SPECIFICITY, INDUCTION, DISRUPTION PHENOTYPE.
  2. "Genome sequence of the nematode C. elegans: a platform for investigating biology."
    The C. elegans sequencing consortium
    Science 282:2012-2018(1998) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA], ALTERNATIVE SPLICING.
    Strain: Bristol N2.
  3. Cited for: INTERACTION WITH VHL-1, HYDROXYLATION AT PRO-621, MUTAGENESIS OF PRO-621.
  4. "Dephosphorylation of cell cycle-regulated proteins correlates with anoxia-induced suspended animation in Caenorhabditis elegans."
    Padilla P.A., Nystul T.G., Zager R.A., Johnson A.C., Roth M.B.
    Mol. Biol. Cell 13:1473-1483(2002) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, DISRUPTION PHENOTYPE.
  5. "HIF-1 is required for heat acclimation in the nematode Caenorhabditis elegans."
    Treinin M., Shliar J., Jiang H., Powell-Coffman J.A., Bromberg Z., Horowitz M.
    Physiol. Genomics 14:17-24(2003) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, INDUCTION, DISRUPTION PHENOTYPE.
  6. "Roles of the HIF-1 hypoxia-inducible factor during hypoxia response in Caenorhabditis elegans."
    Shen C., Nettleton D., Jiang M., Kim S.K., Powell-Coffman J.A.
    J. Biol. Chem. 280:20580-20588(2005) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION.
  7. "Paralysis and killing of Caenorhabditis elegans by enteropathogenic Escherichia coli requires the bacterial tryptophanase gene."
    Anyanful A., Dolan-Livengood J.M., Lewis T., Sheth S., Dezalia M.N., Sherman M.A., Kalman L.V., Benian G.M., Kalman D.
    Mol. Microbiol. 57:988-1007(2005) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, DISRUPTION PHENOTYPE.
  8. "Hypoxia and the HIF-1 transcriptional pathway reorganize a neuronal circuit for oxygen-dependent behavior in Caenorhabditis elegans."
    Chang A.J., Bargmann C.I.
    Proc. Natl. Acad. Sci. U.S.A. 105:7321-7326(2008) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION.
  9. "HIF-1 modulates dietary restriction-mediated lifespan extension via IRE-1 in Caenorhabditis elegans."
    Chen D., Thomas E.L., Kapahi P.
    PLoS Genet. 5:E1000486-E1000486(2009) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, TISSUE SPECIFICITY, DISRUPTION PHENOTYPE.
  10. "Inhibition of respiration extends C. elegans life span via reactive oxygen species that increase HIF-1 activity."
    Lee S.J., Hwang A.B., Kenyon C.
    Curr. Biol. 20:2131-2136(2010) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, DISRUPTION PHENOTYPE.
  11. "Hydrogen sulfide increases hypoxia-inducible factor-1 activity independently of von Hippel-Lindau tumor suppressor-1 in C. elegans."
    Budde M.W., Roth M.B.
    Mol. Biol. Cell 21:212-217(2010) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, SUBCELLULAR LOCATION, INDUCTION, DISRUPTION PHENOTYPE.
  12. "HIF-1 antagonizes p53-mediated apoptosis through a secreted neuronal tyrosinase."
    Sendoel A., Kohler I., Fellmann C., Lowe S.W., Hengartner M.O.
    Nature 465:577-583(2010) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION.
  13. "Hypoxia activates a latent circuit for processing gustatory information in C. elegans."
    Pocock R., Hobert O.
    Nat. Neurosci. 13:610-614(2010) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION.
  14. "C. elegans SWAN-1 Binds to EGL-9 and regulates HIF-1-mediated resistance to the bacterial pathogen Pseudomonas aeruginosa PAO1."
    Shao Z., Zhang Y., Ye Q., Saldanha J.N., Powell-Coffman J.A.
    PLoS Pathog. 6:E1001075-E1001075(2010) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, DISRUPTION PHENOTYPE.
  15. "HIF-1 modulates longevity and healthspan in a temperature-dependent manner."
    Leiser S.F., Begun A., Kaeberlein M.
    Aging Cell 10:318-326(2011) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, DISRUPTION PHENOTYPE.
  16. "Insulin/IGF-1 and hypoxia signaling act in concert to regulate iron homeostasis in Caenorhabditis elegans."
    Ackerman D., Gems D.
    PLoS Genet. 8:E1002498-E1002498(2012) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION.
  17. "EGL-9 controls C. elegans host defense specificity through prolyl hydroxylation-dependent and -independent HIF-1 pathways."
    Luhachack L.G., Visvikis O., Wollenberg A.C., Lacy-Hulbert A., Stuart L.M., Irazoqui J.E.
    PLoS Pathog. 8:E1002798-E1002798(2012) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION.

Entry informationi

Entry nameiHIF1_CAEEL
AccessioniPrimary (citable) accession number: G5EGD2
Secondary accession number(s): G5ECE6
, G5EDZ3, G5EE28, Q8I4D0
Entry historyi
Integrated into UniProtKB/Swiss-Prot: April 18, 2012
Last sequence update: December 14, 2011
Last modified: May 11, 2016
This is version 42 of the entry and version 1 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programCaenorhabditis annotation project

Miscellaneousi

Keywords - Technical termi

Complete proteome, Reference proteome

Documents

  1. Caenorhabditis elegans
    Caenorhabditis elegans: entries, gene names and cross-references to WormBase
  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.