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Protein

Trigger factor

Gene

tig

Organism
Escherichia coli (strain K12)
Status
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli

Functioni

Involved in protein export. Acts as a chaperone by maintaining the newly synthesized secretory and non-secretory proteins in an open conformation. Binds to 3 regions of unfolded substrate PhoA, preferring aromatic and hydrophobic residues, keeping it stretched out and unable to form aggregates (PubMed:24812405). Binds to nascent polypeptide chains via ribosomal protein L23 (PubMed:12226666). Functions as a peptidyl-prolyl cis-trans isomerase in vitro, this activity is dispensible in vivo for chaperone activity.4 Publications

Catalytic activityi

Peptidylproline (omega=180) = peptidylproline (omega=0).1 Publication

GO - Molecular functioni

  • identical protein binding Source: IntAct
  • peptidyl-prolyl cis-trans isomerase activity Source: EcoCyc
  • protein binding involved in protein folding Source: EcoCyc
  • ribosome binding Source: EcoCyc

GO - Biological processi

  • 'de novo' cotranslational protein folding Source: EcoCyc
  • cell cycle Source: UniProtKB-KW
  • cell division Source: UniProtKB-KW
  • protein peptidyl-prolyl isomerization Source: GOC
  • protein transport Source: UniProtKB-HAMAP
  • response to heat Source: EcoCyc
Complete GO annotation...

Keywords - Molecular functioni

Chaperone, Isomerase, Rotamase

Keywords - Biological processi

Cell cycle, Cell division

Enzyme and pathway databases

BioCyciEcoCyc:EG11003-MONOMER.
ECOL316407:JW0426-MONOMER.
MetaCyc:EG11003-MONOMER.

Names & Taxonomyi

Protein namesi
Recommended name:
Trigger factor (EC:5.2.1.81 Publication)
Short name:
TF
Alternative name(s):
PPIase
Gene namesi
Name:tig
Ordered Locus Names:b0436, JW0426
OrganismiEscherichia coli (strain K12)
Taxonomic identifieri83333 [NCBI]
Taxonomic lineageiBacteriaProteobacteriaGammaproteobacteriaEnterobacterialesEnterobacteriaceaeEscherichia
ProteomesiUP000000318 Componenti: Chromosome UP000000625 Componenti: Chromosome

Organism-specific databases

EcoGeneiEG11003. tig.

Subcellular locationi

  • Cytoplasm 1 Publication

  • Note: About half TF is bound to the ribosome near the polypeptide exit tunnel while the other half is free in the cytoplasm.1 Publication

GO - Cellular componenti

  • cytosol Source: UniProtKB
  • membrane Source: UniProtKB
Complete GO annotation...

Keywords - Cellular componenti

Cytoplasm

Pathology & Biotechi

Disruption phenotypei

Non-essential; synthetic lethality is seen in a triple tig-dnaK-dnaJ disruption, although this depends on temperature (triple disruptions grow slowly at 20 and 34 degrees Celsius but not at all at 43 degrees) and strain background.1 Publication

Mutagenesis

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Mutagenesisi44 – 463FRK → AAA: Decreases association with ribosomes. 1 Publication
Mutagenesisi140 – 1401M → E: Significantly decreases antiaggregation activity. 1 Publication
Mutagenesisi374 – 38714MASAY…EVIEF → AASAAEDPKEAIEA: Significantly decreased affinity for substrate PhoA, significantly decreases antiaggregation activity. 1 PublicationAdd
BLAST

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Chaini1 – 432432Trigger factorPRO_0000179347Add
BLAST

Proteomic databases

PaxDbiP0A850.
PRIDEiP0A850.

2D gel databases

SWISS-2DPAGEP0A850.

Expressioni

Gene expression databases

GenevestigatoriP0A850.

Interactioni

Subunit structurei

Homodimer and monomer. In vivo most of the ribosomes are in complex with monomeric TF (PubMed:12452438); binding as a dimer has also been suggested (PubMed:12581648). Uncomplexed TF is in a monomer-dimer equilibrium with approximately two thirds of TF existing in a dimeric state; binding to substrate PhoA induces monomerization, 3 TF monomers bind somewhat independently to a single substrate molecule (PubMed:12452438, PubMed:24812405). TF and SRP can simultaneously bind to ribosomes; TF binding is abolished when SRP is bound to FtsY in the presence of a non-hydrolyzable GTP analog (PubMed:15148364). Contacts ribosomal proteins L23 and L29 (PubMed:12226666).5 Publications

Binary interactionsi

WithEntry#Exp.IntActNotes
itself2EBI-544862,EBI-544862
ompAP0A9103EBI-544862,EBI-371347
rpsGP023593EBI-544862,EBI-543074

Protein-protein interaction databases

DIPiDIP-36226N.
IntActiP0A850. 125 interactions.
MINTiMINT-1225982.
STRINGi511145.b0436.

Structurei

Secondary structure

1
432
Legend: HelixTurnBeta strand
Show more details
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Beta strandi2 – 76Combined sources
Beta strandi12 – 198Combined sources
Helixi21 – 3616Combined sources
Helixi42 – 443Combined sources
Beta strandi46 – 483Combined sources
Helixi51 – 8131Combined sources
Beta strandi87 – 948Combined sources
Beta strandi99 – 1013Combined sources
Beta strandi103 – 1108Combined sources
Turni120 – 1223Combined sources
Beta strandi127 – 1293Combined sources
Helixi134 – 14714Combined sources
Beta strandi155 – 1573Combined sources
Beta strandi163 – 1664Combined sources
Beta strandi168 – 1747Combined sources
Beta strandi183 – 1886Combined sources
Helixi198 – 2014Combined sources
Beta strandi202 – 2043Combined sources
Beta strandi210 – 2167Combined sources
Turni224 – 2263Combined sources
Beta strandi230 – 2367Combined sources
Helixi250 – 2534Combined sources
Turni254 – 2574Combined sources
Helixi263 – 29735Combined sources
Helixi304 – 31916Combined sources
Turni320 – 3234Combined sources
Helixi334 – 3363Combined sources
Helixi338 – 35720Combined sources
Helixi364 – 37512Combined sources
Helixi381 – 39010Combined sources
Helixi392 – 41221Combined sources
Beta strandi419 – 4213Combined sources
Helixi424 – 4274Combined sources

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
1L1PNMR-A148-249[»]
1OMSX-ray2.30A/B/C1-118[»]
1P9YX-ray2.15A/B1-118[»]
1W26X-ray2.70A/B1-432[»]
1W2BX-ray3.5051-144[»]
2MLXNMR-A1-432[»]
2MLYNMR-A1-432[»]
2MLZNMR-A1-432[»]
2VRHelectron microscopy19.00A1-432[»]
ProteinModelPortaliP0A850.
SMRiP0A850. Positions 1-432.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiP0A850.

Family & Domainsi

Domains and Repeats

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Domaini161 – 24686PPIase FKBP-typeAdd
BLAST

Region

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Regioni1 – 112112Ribosome-binding1 PublicationAdd
BLAST
Regioni148 – 251104Dispensable for chaperone activity, although its removal significantly decreases antiaggregation activity2 PublicationsAdd
BLAST

Domaini

Consists of 3 domains; the N-terminus (residues 1-112) binds the ribosome, the middle domain (residues 150-246) has PPIase activity, while the discontinuous C-terminus (residues 113-149 and 247-432) binds substrate and has intrinsic chaperone activity on its own.2 Publications

Sequence similaritiesi

Belongs to the FKBP-type PPIase family. Tig subfamily.Curated
Contains 1 PPIase FKBP-type domain.Curated

Phylogenomic databases

eggNOGiCOG0544.
HOGENOMiHOG000218239.
InParanoidiP0A850.
KOiK03545.
OMAiKITFIID.
OrthoDBiEOG63VBX3.
PhylomeDBiP0A850.

Family and domain databases

Gene3Di1.10.3120.10. 1 hit.
3.30.70.1050. 1 hit.
HAMAPiMF_00303. Trigger_factor_Tig.
InterProiIPR001179. PPIase_FKBP_dom.
IPR005215. Trig_fac.
IPR008880. Trigger_fac_C.
IPR008881. Trigger_fac_ribosome-bd_bac.
IPR027304. Trigger_fact/SurA_dom.
[Graphical view]
PfamiPF00254. FKBP_C. 1 hit.
PF05698. Trigger_C. 1 hit.
PF05697. Trigger_N. 1 hit.
[Graphical view]
PIRSFiPIRSF003095. Trigger_factor. 1 hit.
SUPFAMiSSF102735. SSF102735. 1 hit.
SSF109998. SSF109998. 1 hit.
TIGRFAMsiTIGR00115. tig. 1 hit.
PROSITEiPS50059. FKBP_PPIASE. 1 hit.
[Graphical view]

Sequencei

Sequence statusi: Complete.

P0A850-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MQVSVETTQG LGRRVTITIA ADSIETAVKS ELVNVAKKVR IDGFRKGKVP
60 70 80 90 100
MNIVAQRYGA SVRQDVLGDL MSRNFIDAII KEKINPAGAP TYVPGEYKLG
110 120 130 140 150
EDFTYSVEFE VYPEVELQGL EAIEVEKPIV EVTDADVDGM LDTLRKQQAT
160 170 180 190 200
WKEKDGAVEA EDRVTIDFTG SVDGEEFEGG KASDFVLAMG QGRMIPGFED
210 220 230 240 250
GIKGHKAGEE FTIDVTFPEE YHAENLKGKA AKFAINLKKV EERELPELTA
260 270 280 290 300
EFIKRFGVED GSVEGLRAEV RKNMERELKS AIRNRVKSQA IEGLVKANDI
310 320 330 340 350
DVPAALIDSE IDVLRRQAAQ RFGGNEKQAL ELPRELFEEQ AKRRVVVGLL
360 370 380 390 400
LGEVIRTNEL KADEERVKGL IEEMASAYED PKEVIEFYSK NKELMDNMRN
410 420 430
VALEEQAVEA VLAKAKVTEK ETTFNELMNQ QA
Length:432
Mass (Da):48,193
Last modified:June 7, 2005 - v1
Checksum:i42C3E3C335074164
GO

Experimental Info

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sequence conflicti118 – 1181Q → E in AAA62791 (PubMed:2211496).Curated
Sequence conflicti279 – 2879KSAIRNRVK → RAPSVTALS in AAA62791 (PubMed:2211496).Curated

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
M34066 Genomic DNA. Translation: AAA62791.1.
U00096 Genomic DNA. Translation: AAC73539.1.
AP009048 Genomic DNA. Translation: BAE76216.1.
U82664 Genomic DNA. Translation: AAB40192.1.
X17642 Genomic DNA. Translation: CAA35634.1.
J05534 Genomic DNA. Translation: AAA23587.1.
PIRiD64773.
RefSeqiNP_414970.1. NC_000913.3.

Genome annotation databases

EnsemblBacteriaiAAC73539; AAC73539; b0436.
BAE76216; BAE76216; BAE76216.
GeneIDi945081.
KEGGiecj:Y75_p0424.
eco:b0436.
PATRICi32116025. VBIEscCol129921_0454.

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
M34066 Genomic DNA. Translation: AAA62791.1.
U00096 Genomic DNA. Translation: AAC73539.1.
AP009048 Genomic DNA. Translation: BAE76216.1.
U82664 Genomic DNA. Translation: AAB40192.1.
X17642 Genomic DNA. Translation: CAA35634.1.
J05534 Genomic DNA. Translation: AAA23587.1.
PIRiD64773.
RefSeqiNP_414970.1. NC_000913.3.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
1L1PNMR-A148-249[»]
1OMSX-ray2.30A/B/C1-118[»]
1P9YX-ray2.15A/B1-118[»]
1W26X-ray2.70A/B1-432[»]
1W2BX-ray3.5051-144[»]
2MLXNMR-A1-432[»]
2MLYNMR-A1-432[»]
2MLZNMR-A1-432[»]
2VRHelectron microscopy19.00A1-432[»]
ProteinModelPortaliP0A850.
SMRiP0A850. Positions 1-432.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

DIPiDIP-36226N.
IntActiP0A850. 125 interactions.
MINTiMINT-1225982.
STRINGi511145.b0436.

2D gel databases

SWISS-2DPAGEP0A850.

Proteomic databases

PaxDbiP0A850.
PRIDEiP0A850.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsemblBacteriaiAAC73539; AAC73539; b0436.
BAE76216; BAE76216; BAE76216.
GeneIDi945081.
KEGGiecj:Y75_p0424.
eco:b0436.
PATRICi32116025. VBIEscCol129921_0454.

Organism-specific databases

EchoBASEiEB0996.
EcoGeneiEG11003. tig.

Phylogenomic databases

eggNOGiCOG0544.
HOGENOMiHOG000218239.
InParanoidiP0A850.
KOiK03545.
OMAiKITFIID.
OrthoDBiEOG63VBX3.
PhylomeDBiP0A850.

Enzyme and pathway databases

BioCyciEcoCyc:EG11003-MONOMER.
ECOL316407:JW0426-MONOMER.
MetaCyc:EG11003-MONOMER.

Miscellaneous databases

EvolutionaryTraceiP0A850.
PROiP0A850.

Gene expression databases

GenevestigatoriP0A850.

Family and domain databases

Gene3Di1.10.3120.10. 1 hit.
3.30.70.1050. 1 hit.
HAMAPiMF_00303. Trigger_factor_Tig.
InterProiIPR001179. PPIase_FKBP_dom.
IPR005215. Trig_fac.
IPR008880. Trigger_fac_C.
IPR008881. Trigger_fac_ribosome-bd_bac.
IPR027304. Trigger_fact/SurA_dom.
[Graphical view]
PfamiPF00254. FKBP_C. 1 hit.
PF05698. Trigger_C. 1 hit.
PF05697. Trigger_N. 1 hit.
[Graphical view]
PIRSFiPIRSF003095. Trigger_factor. 1 hit.
SUPFAMiSSF102735. SSF102735. 1 hit.
SSF109998. SSF109998. 1 hit.
TIGRFAMsiTIGR00115. tig. 1 hit.
PROSITEiPS50059. FKBP_PPIASE. 1 hit.
[Graphical view]
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "Trigger factor depletion or overproduction causes defective cell division but does not block protein export."
    Guthrie B., Wickner W.
    J. Bacteriol. 172:5555-5562(1990) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA], PARTIAL PROTEIN SEQUENCE.
    Strain: K12.
  2. "Sequence of minutes 4-25 of Escherichia coli."
    Chung E., Allen E., Araujo R., Aparicio A.M., Davis K., Duncan M., Federspiel N., Hyman R., Kalman S., Komp C., Kurdi O., Lew H., Lin D., Namath A., Oefner P., Roberts D., Schramm S., Davis R.W.
    Submitted (JAN-1997) to the EMBL/GenBank/DDBJ databases
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    Strain: K12 / MG1655 / ATCC 47076.
  3. Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    Strain: K12 / MG1655 / ATCC 47076.
  4. "Highly accurate genome sequences of Escherichia coli K-12 strains MG1655 and W3110."
    Hayashi K., Morooka N., Yamamoto Y., Fujita K., Isono K., Choi S., Ohtsubo E., Baba T., Wanner B.L., Mori H., Horiuchi T.
    Mol. Syst. Biol. 2:E1-E5(2006) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    Strain: K12 / W3110 / ATCC 27325 / DSM 5911.
  5. "Induction of a growth-phase-dependent promoter triggers transcription of bolA, an Escherichia coli morphogene."
    Aldea M., Garrido T., Hernandez-Chico C., Vicente M., Kushner S.R.
    EMBO J. 8:3923-3931(1989) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA] OF 1-145.
  6. "ProOmpA is stabilized for membrane translocation by either purified E. coli trigger factor or canine signal recognition particle."
    Crooke E., Guthrie B., Lecker S., Lill R., Wickner W.
    Cell 54:1003-1011(1988) [PubMed] [Europe PMC] [Abstract]
    Cited for: PROTEIN SEQUENCE OF 1-13.
  7. "Comparing the predicted and observed properties of proteins encoded in the genome of Escherichia coli K-12."
    Link A.J., Robison K., Church G.M.
    Electrophoresis 18:1259-1313(1997) [PubMed] [Europe PMC] [Abstract]
    Cited for: PROTEIN SEQUENCE OF 1-21 AND 38-58.
    Strain: K12 / EMG2.
  8. "Escherichia coli trigger factor is a prolyl isomerase that associates with nascent polypeptide chains."
    Hesterkamp T., Hauser S., Lutcke H., Bukau B.
    Proc. Natl. Acad. Sci. U.S.A. 93:4437-4441(1996) [PubMed] [Europe PMC] [Abstract]
    Cited for: PROTEIN SEQUENCE OF 1-7, FUNCTION AS A PPIASE, SUBCELLULAR LOCATION, RIBOSOME-BINDING.
  9. "An 11.8 kDa proteolytic fragment of the E. coli trigger factor represents the domain carrying the peptidyl-prolyl cis/trans isomerase activity."
    Stoller G., Tradler T., Ruecknagel K.P., Rahfeld J.-U., Fischer G.
    FEBS Lett. 384:117-122(1996) [PubMed] [Europe PMC] [Abstract]
    Cited for: PROTEIN SEQUENCE OF 145-174.
  10. "Sequence and structure of Clp P, the proteolytic component of the ATP-dependent Clp protease of Escherichia coli."
    Maurizi M.R., Clark W.P., Katayama Y., Rudikoff S., Pumphrey J., Bowers B., Gottesman S.
    J. Biol. Chem. 265:12536-12545(1990) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA] OF 390-432.
  11. "Early events in preprotein recognition in E. coli: interaction of SRP and trigger factor with nascent polypeptides."
    Valent Q.A., Kendall D.A., High S., Kusters R., Oudega B., Luirink J.
    EMBO J. 14:5494-5505(1995) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION.
  12. "Escherichia coli proteome analysis using the gene-protein database."
    VanBogelen R.A., Abshire K.Z., Moldover B., Olson E.R., Neidhardt F.C.
    Electrophoresis 18:1243-1251(1997) [PubMed] [Europe PMC] [Abstract]
    Cited for: IDENTIFICATION BY 2D-GEL.
  13. "Three-state equilibrium of Escherichia coli trigger factor."
    Patzelt H., Kramer G., Rauch T., Schonfeld H.J., Bukau B., Deuerling E.
    Biol. Chem. 383:1611-1619(2002) [PubMed] [Europe PMC] [Abstract]
    Cited for: SUBUNIT.
  14. Cited for: BINDING TO RIBOSOMAL PROTEINS L23 AND L29, MUTAGENESIS OF 44-PHE--LYS-46.
    Strain: K12 / MC4100 / ATCC 35695 / DSM 6574.
  15. "Interplay of signal recognition particle and trigger factor at L23 near the nascent chain exit site on the Escherichia coli ribosome."
    Ullers R.S., Houben E.N.G., Raine A., ten Hagen-Jongman C.M., Ehrenberg M., Brunner J., Oudega B., Harms N., Luirink J.
    J. Cell Biol. 161:679-684(2003) [PubMed] [Europe PMC] [Abstract]
    Cited for: CROSS-LINKS TO NASCENT PROTEIN CHAINS.
    Strain: K12 / MC4100 / ATCC 35695 / DSM 6574.
  16. "In vivo analysis of the overlapping functions of DnaK and trigger factor."
    Genevaux P., Keppel F., Schwager F., Langendijk-Genevaux P.S., Hartl F.U., Georgopoulos C.
    EMBO Rep. 5:195-200(2004) [PubMed] [Europe PMC] [Abstract]
    Cited for: DOMAIN, DISPENSABILITY OF PPIASE FOR CHAPERONE FUNCTION, DISRUPTION PHENOTYPE.
    Strain: K12 / MC4100 / ATCC 35695 / DSM 6574.
  17. "Localization of the trigger factor binding site on the ribosomal 50S subunit."
    Blaha G., Wilson D.N., Stoller G., Fischer G., Willumeit R., Nierhaus K.H.
    J. Mol. Biol. 326:887-897(2003) [PubMed] [Europe PMC] [Abstract]
    Cited for: MAY BIND TO THE RIBOSOME AS A DIMER.
    Strain: MRE-600.
  18. "Trigger factor binds to ribosome-signal-recognition particle (SRP) complexes and is excluded by binding of the SRP receptor."
    Buskiewicz I., Deuerling E., Gu S.-Q., Joeckel J., Rodnina M.V., Bukau B., Wintermeyer W.
    Proc. Natl. Acad. Sci. U.S.A. 101:7902-7906(2004) [PubMed] [Europe PMC] [Abstract]
    Cited for: SIMULTANEOUS BINDING OF TRIGGER FACTOR AND SRP TO THE RIBOSOME.
    Strain: MRE-600.
  19. "Structural basis for protein antiaggregation activity of the trigger factor chaperone."
    Saio T., Guan X., Rossi P., Economou A., Kalodimos C.G.
    Science 344:1250494-1250494(2014) [PubMed] [Europe PMC] [Abstract]
    Cited for: STRUCTURE BY NMR IN COMPLEX WITH PHOA SUBSTRATE, FUNCTION, SUBUNIT, DOMAIN, MUTAGENESIS OF MET-140 AND 374-MET--PHE-387.

Entry informationi

Entry nameiTIG_ECOLI
AccessioniPrimary (citable) accession number: P0A850
Secondary accession number(s): P15299
, P22257, P77603, Q2MBZ0
Entry historyi
Integrated into UniProtKB/Swiss-Prot: June 7, 2005
Last sequence update: June 7, 2005
Last modified: May 27, 2015
This is version 99 of the entry and version 1 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programProkaryotic Protein Annotation Program

Miscellaneousi

Keywords - Technical termi

3D-structure, Complete proteome, Direct protein sequencing, Reference proteome

Documents

  1. Escherichia coli
    Escherichia coli (strain K12): entries and cross-references to EcoGene
  2. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  3. 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.