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Protein

Ribosomal protein S6 kinase beta-1

Gene

Rps6kb1

Organism
Mus musculus (Mouse)
Status
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli

Functioni

Serine/threonine-protein kinase that acts downstream of mTOR signaling in response to growth factors and nutrients to promote cell proliferation, cell growth and cell cycle progression. Regulates protein synthesis through phosphorylation of EIF4B, RPS6 and EEF2K, and contributes to cell survival by repressing the pro-apoptotic function of BAD. Under conditions of nutrient depletion, the inactive form associates with the EIF3 translation initiation complex. Upon mitogenic stimulation, phosphorylation by the mammalian target of rapamycin complex 1 (mTORC1) leads to dissociation from the EIF3 complex and activation. The active form then phosphorylates and activates several substrates in the preinitiation complex, including the EIF2B complex and the cap-binding complex component EIF4B. Also controls translation initiation by phosphorylating a negative regulator of EIF4A, PDCD4, targeting it for ubiquitination and subsequent proteolysis. Promotes initiation of the pioneer round of protein synthesis by phosphorylating POLDIP3/SKAR. In response to IGF1, activates translation elongation by phosphorylating EEF2 kinase (EEF2K), which leads to its inhibition and thus activation of EEF2. Also plays a role in feedback regulation of mTORC2 by mTORC1 by phosphorylating RICTOR, resulting in the inhibition of mTORC2 and AKT1 signaling. Mediates cell survival by phosphorylating the pro-apoptotic protein BAD and suppressing its pro-apoptotic function. Phosphorylates mitochondrial RMP leading to dissociation of a RMP:PPP1CC complex. The free mitochondrial PPP1CC can then dephosphorylate RPS6KB1 at Thr-412, which is proposed to be a negative feedback mechanism for the RPS6KB1 anti-apoptotic function. Mediates TNF-alpha-induced insulin resistance by phosphorylating IRS1 at multiple serine residues, resulting in accelerated degradation of IRS1. In cells lacking functional TSC1-2 complex, constitutively phosphorylates and inhibits GSK3B. May be involved in cytoskeletal rearrangement through binding to neurabin. Phosphorylates and activates the pyrimidine biosynthesis enzyme CAD, downstream of MTOR (By similarity).By similarity

Catalytic activityi

ATP + a protein = ADP + a phosphoprotein.

Enzyme regulationi

Activation requires multiple phosphorylation events on serine/threonine residues. Activation appears to be first mediated by phosphorylation of multiple sites in the autoinhibitory domain, which facilitates phosphorylation at Thr-412, disrupting the autoinhibitory mechanism and allowing phosphorylation of Thr-252 by PDPK1. The active conformation of the kinase is believed to be stabilized by a mechanism involving three conserved phosphorylation sites located in the kinase domain activation loop (Thr-252) and in the AGC-kinase C-terminal domain (Ser-394 in the middle of the tail/linker region and Thr-412 within a hydrophobic motif at its end). Activated by mTORC1; isoform Alpha I and isoform Alpha II are sensitive to rapamycin, which inhibits activating phosphorylation at Thr-412. Activated by PDPK1 (By similarity).By similarity

Sites

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Binding sitei123 – 1231ATPPROSITE-ProRule annotation
Active sitei218 – 2181Proton acceptorPROSITE-ProRule annotation

Regions

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Nucleotide bindingi97 – 1059ATPPROSITE-ProRule annotation

GO - Molecular functioni

GO - Biological processi

Complete GO annotation...

Keywords - Molecular functioni

Kinase, Serine/threonine-protein kinase, Transferase

Keywords - Biological processi

Apoptosis, Cell cycle, Translation regulation

Keywords - Ligandi

ATP-binding, Nucleotide-binding

Enzyme and pathway databases

ReactomeiREACT_283781. S6K1 signalling.
REACT_333210. S6K1-mediated signalling.

Names & Taxonomyi

Protein namesi
Recommended name:
Ribosomal protein S6 kinase beta-1 (EC:2.7.11.1)
Short name:
S6K-beta-1
Short name:
S6K1
Alternative name(s):
70 kDa ribosomal protein S6 kinase 1
Short name:
P70S6K1
Short name:
p70-S6K 1
Ribosomal protein S6 kinase I
Short name:
S6K
p70 ribosomal S6 kinase alpha
Short name:
p70 S6 kinase alpha
Short name:
p70 S6K-alpha
Short name:
p70 S6KA
Gene namesi
Name:Rps6kb1
OrganismiMus musculus (Mouse)
Taxonomic identifieri10090 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresGliresRodentiaSciurognathiMuroideaMuridaeMurinaeMusMus
ProteomesiUP000000589 Componenti: Chromosome 11

Organism-specific databases

MGIiMGI:1270849. Rps6kb1.

Subcellular locationi

GO - Cellular componenti

Complete GO annotation...

Keywords - Cellular componenti

Cell junction, Cytoplasm, Membrane, Mitochondrion, Mitochondrion outer membrane, Synapse, Synaptosome

Pathology & Biotechi

Disruption phenotypei

Impairment of body growth. Lethal in combination with Rps6kb2 deficiency.1 Publication

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Chaini1 – 525525Ribosomal protein S6 kinase beta-1PRO_0000024344Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei252 – 2521Phosphothreonine; by PDPK1By similarity
Modified residuei394 – 3941PhosphoserineBy similarity
Modified residuei412 – 4121Phosphothreonine; by MTOR, NEK6 and NEK7By similarity
Modified residuei434 – 4341PhosphoserineBy similarity
Modified residuei441 – 4411PhosphoserineBy similarity
Modified residuei444 – 4441PhosphothreonineBy similarity
Modified residuei447 – 4471PhosphoserineBy similarity
Modified residuei452 – 4521PhosphoserineBy similarity
Modified residuei516 – 5161N6-acetyllysineBy similarity

Post-translational modificationi

Phosphorylation at Thr-412 is regulated by mTORC1. The phosphorylation at this site is maintained by an agonist-dependent autophosphorylation mechanism. Activated by phosphorylation at Thr-252 by PDPK1. Dephosphorylation by PPP1CC at Thr-412 in mitochondrion (By similarity).By similarity

Keywords - PTMi

Acetylation, Phosphoprotein

Proteomic databases

MaxQBiQ8BSK8.
PaxDbiQ8BSK8.
PRIDEiQ8BSK8.

PTM databases

PhosphoSiteiQ8BSK8.

Expressioni

Gene expression databases

BgeeiQ8BSK8.
CleanExiMM_RPS6KB1.
ExpressionAtlasiQ8BSK8. baseline and differential.
GenevisibleiQ8BSK8. MM.

Interactioni

Subunit structurei

Interacts with PPP1R9A/neurabin-1 (By similarity). Interacts with RPTOR. Interacts with IRS1. Interacts with EIF3B and EIF3C. Interacts with POLDIP3 and TRAF4 (By similarity).By similarity

Binary interactionsi

WithEntry#Exp.IntActNotes
Mdm2P238042EBI-646423,EBI-641788

Protein-protein interaction databases

BioGridi215408. 10 interactions.
IntActiQ8BSK8. 5 interactions.
MINTiMINT-5092082.
STRINGi10090.ENSMUSP00000119715.

Structurei

3D structure databases

ProteinModelPortaliQ8BSK8.
SMRiQ8BSK8. Positions 81-417.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Domains and Repeats

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Domaini91 – 352262Protein kinasePROSITE-ProRule annotationAdd
BLAST
Domaini353 – 42371AGC-kinase C-terminalAdd
BLAST

Region

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Regioni424 – 525102Autoinhibitory domainAdd
BLAST

Motif

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Motifi28 – 325TOS motif

Domaini

The autoinhibitory domain is believed to block phosphorylation within the AGC-kinase C-terminal domain and the activation loop.By similarity
The TOS (TOR signaling) motif is essential for activation by mTORC1.By similarity

Sequence similaritiesi

Contains 1 AGC-kinase C-terminal domain.Curated
Contains 1 protein kinase domain.PROSITE-ProRule annotation

Phylogenomic databases

eggNOGiCOG0515.
GeneTreeiENSGT00770000120449.
HOGENOMiHOG000233033.
HOVERGENiHBG108317.
InParanoidiQ8BSK8.
KOiK04688.
OMAiHRANRMP.
OrthoDBiEOG7B8S38.
TreeFamiTF313438.

Family and domain databases

InterProiIPR000961. AGC-kinase_C.
IPR011009. Kinase-like_dom.
IPR017892. Pkinase_C.
IPR000719. Prot_kinase_dom.
IPR017441. Protein_kinase_ATP_BS.
IPR016238. Ribosomal_S6_kinase.
IPR002290. Ser/Thr_dual-sp_kinase.
IPR008271. Ser/Thr_kinase_AS.
[Graphical view]
PfamiPF00069. Pkinase. 1 hit.
PF00433. Pkinase_C. 1 hit.
[Graphical view]
PIRSFiPIRSF000605. Ribsml_S6_kin_1. 1 hit.
SMARTiSM00133. S_TK_X. 1 hit.
SM00220. S_TKc. 1 hit.
[Graphical view]
SUPFAMiSSF56112. SSF56112. 1 hit.
PROSITEiPS51285. AGC_KINASE_CTER. 1 hit.
PS00107. PROTEIN_KINASE_ATP. 1 hit.
PS50011. PROTEIN_KINASE_DOM. 1 hit.
PS00108. PROTEIN_KINASE_ST. 1 hit.
[Graphical view]

Sequences (2)i

Sequence statusi: Complete.

This entry describes 2 isoformsi produced by alternative initiation. AlignAdd to basket

Isoform Alpha I (identifier: Q8BSK8-1) [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
MRRRRRRDGF YLAPDFRHRE AEDMAGVFDI DLDQPEDAGS EDELEEGGQL
60 70 80 90 100
NESMDHGGVG PYELGMEHCE KFEISETSVN RGPEKIRPEC FELLRVLGKG
110 120 130 140 150
GYGKVFQVRK VTGANTGKIF AMKVLKKAMI VRNAKDTAHT KAERNILEEV
160 170 180 190 200
KHPFIVDLIY AFQTGGKLYL ILEYLSGGEL FMQLEREGIF MEDTACFYLA
210 220 230 240 250
EISMALGHLH QKGIIYRDLK PENIMLNHQG HVKLTDFGLC KESIHDGTVT
260 270 280 290 300
HTFCGTIEYM APEILMRSGH NRAVDWWSLG ALMYDMLTGA PPFTGENRKK
310 320 330 340 350
TIDKILKCKL NLPPYLTQEA RDLLKKLLKR NAASRLGAGP GDAGEVQAHP
360 370 380 390 400
FFRHINWEEL LARKVEPPFK PLLQSEEDVS QFDSKFTRQT PVDSPDDSTL
410 420 430 440 450
SESANQVFLG FTYVAPSVLE SVKEKFSFEP KIRSPRRFIG SPRTPVSPVK
460 470 480 490 500
FSPGDFWGRG ASASTANPQT PVEYPMETSG IEQMDVTVSG EASAPLPIRQ
510 520
PNSGPYKKQA FPMISKRPEH LRMNL
Length:525
Mass (Da):59,146
Last modified:July 27, 2011 - v2
Checksum:i5B3C09F6BB365EE2
GO
Isoform Alpha II (identifier: Q8BSK8-2) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     1-23: Missing.

Show »
Length:502
Mass (Da):56,157
Checksum:i5AE6CF3FCAAE8B83
GO

Experimental Info

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sequence conflicti60 – 601G → E in BAC28000 (PubMed:16141072).Curated

Alternative sequence

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Alternative sequencei1 – 2323Missing in isoform Alpha II. CuratedVSP_018840Add
BLAST

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AK032724 mRNA. Translation: BAC28000.1.
AL604063 Genomic DNA. Translation: CAI25799.1.
CH466556 Genomic DNA. Translation: EDL15788.1.
BC038491 mRNA. Translation: AAH38491.1.
CCDSiCCDS48875.1. [Q8BSK8-1]
RefSeqiNP_001107806.1. NM_001114334.1. [Q8BSK8-1]
UniGeneiMm.394280.
Mm.446624.
Mm.479484.

Genome annotation databases

EnsembliENSMUST00000154617; ENSMUSP00000119715; ENSMUSG00000020516. [Q8BSK8-1]
GeneIDi72508.
KEGGimmu:72508.
UCSCiuc007ksn.2. mouse. [Q8BSK8-1]

Keywords - Coding sequence diversityi

Alternative initiation

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
AK032724 mRNA. Translation: BAC28000.1.
AL604063 Genomic DNA. Translation: CAI25799.1.
CH466556 Genomic DNA. Translation: EDL15788.1.
BC038491 mRNA. Translation: AAH38491.1.
CCDSiCCDS48875.1. [Q8BSK8-1]
RefSeqiNP_001107806.1. NM_001114334.1. [Q8BSK8-1]
UniGeneiMm.394280.
Mm.446624.
Mm.479484.

3D structure databases

ProteinModelPortaliQ8BSK8.
SMRiQ8BSK8. Positions 81-417.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi215408. 10 interactions.
IntActiQ8BSK8. 5 interactions.
MINTiMINT-5092082.
STRINGi10090.ENSMUSP00000119715.

Chemistry

ChEMBLiCHEMBL5429.

PTM databases

PhosphoSiteiQ8BSK8.

Proteomic databases

MaxQBiQ8BSK8.
PaxDbiQ8BSK8.
PRIDEiQ8BSK8.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENSMUST00000154617; ENSMUSP00000119715; ENSMUSG00000020516. [Q8BSK8-1]
GeneIDi72508.
KEGGimmu:72508.
UCSCiuc007ksn.2. mouse. [Q8BSK8-1]

Organism-specific databases

CTDi6198.
MGIiMGI:1270849. Rps6kb1.

Phylogenomic databases

eggNOGiCOG0515.
GeneTreeiENSGT00770000120449.
HOGENOMiHOG000233033.
HOVERGENiHBG108317.
InParanoidiQ8BSK8.
KOiK04688.
OMAiHRANRMP.
OrthoDBiEOG7B8S38.
TreeFamiTF313438.

Enzyme and pathway databases

ReactomeiREACT_283781. S6K1 signalling.
REACT_333210. S6K1-mediated signalling.

Miscellaneous databases

ChiTaRSiRps6kb1. mouse.
NextBioi336366.
PROiQ8BSK8.
SOURCEiSearch...

Gene expression databases

BgeeiQ8BSK8.
CleanExiMM_RPS6KB1.
ExpressionAtlasiQ8BSK8. baseline and differential.
GenevisibleiQ8BSK8. MM.

Family and domain databases

InterProiIPR000961. AGC-kinase_C.
IPR011009. Kinase-like_dom.
IPR017892. Pkinase_C.
IPR000719. Prot_kinase_dom.
IPR017441. Protein_kinase_ATP_BS.
IPR016238. Ribosomal_S6_kinase.
IPR002290. Ser/Thr_dual-sp_kinase.
IPR008271. Ser/Thr_kinase_AS.
[Graphical view]
PfamiPF00069. Pkinase. 1 hit.
PF00433. Pkinase_C. 1 hit.
[Graphical view]
PIRSFiPIRSF000605. Ribsml_S6_kin_1. 1 hit.
SMARTiSM00133. S_TK_X. 1 hit.
SM00220. S_TKc. 1 hit.
[Graphical view]
SUPFAMiSSF56112. SSF56112. 1 hit.
PROSITEiPS51285. AGC_KINASE_CTER. 1 hit.
PS00107. PROTEIN_KINASE_ATP. 1 hit.
PS50011. PROTEIN_KINASE_DOM. 1 hit.
PS00108. PROTEIN_KINASE_ST. 1 hit.
[Graphical view]
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "The transcriptional landscape of the mammalian genome."
    Carninci P., Kasukawa T., Katayama S., Gough J., Frith M.C., Maeda N., Oyama R., Ravasi T., Lenhard B., Wells C., Kodzius R., Shimokawa K., Bajic V.B., Brenner S.E., Batalov S., Forrest A.R., Zavolan M., Davis M.J.
    , Wilming L.G., Aidinis V., Allen J.E., Ambesi-Impiombato A., Apweiler R., Aturaliya R.N., Bailey T.L., Bansal M., Baxter L., Beisel K.W., Bersano T., Bono H., Chalk A.M., Chiu K.P., Choudhary V., Christoffels A., Clutterbuck D.R., Crowe M.L., Dalla E., Dalrymple B.P., de Bono B., Della Gatta G., di Bernardo D., Down T., Engstrom P., Fagiolini M., Faulkner G., Fletcher C.F., Fukushima T., Furuno M., Futaki S., Gariboldi M., Georgii-Hemming P., Gingeras T.R., Gojobori T., Green R.E., Gustincich S., Harbers M., Hayashi Y., Hensch T.K., Hirokawa N., Hill D., Huminiecki L., Iacono M., Ikeo K., Iwama A., Ishikawa T., Jakt M., Kanapin A., Katoh M., Kawasawa Y., Kelso J., Kitamura H., Kitano H., Kollias G., Krishnan S.P., Kruger A., Kummerfeld S.K., Kurochkin I.V., Lareau L.F., Lazarevic D., Lipovich L., Liu J., Liuni S., McWilliam S., Madan Babu M., Madera M., Marchionni L., Matsuda H., Matsuzawa S., Miki H., Mignone F., Miyake S., Morris K., Mottagui-Tabar S., Mulder N., Nakano N., Nakauchi H., Ng P., Nilsson R., Nishiguchi S., Nishikawa S., Nori F., Ohara O., Okazaki Y., Orlando V., Pang K.C., Pavan W.J., Pavesi G., Pesole G., Petrovsky N., Piazza S., Reed J., Reid J.F., Ring B.Z., Ringwald M., Rost B., Ruan Y., Salzberg S.L., Sandelin A., Schneider C., Schoenbach C., Sekiguchi K., Semple C.A., Seno S., Sessa L., Sheng Y., Shibata Y., Shimada H., Shimada K., Silva D., Sinclair B., Sperling S., Stupka E., Sugiura K., Sultana R., Takenaka Y., Taki K., Tammoja K., Tan S.L., Tang S., Taylor M.S., Tegner J., Teichmann S.A., Ueda H.R., van Nimwegen E., Verardo R., Wei C.L., Yagi K., Yamanishi H., Zabarovsky E., Zhu S., Zimmer A., Hide W., Bult C., Grimmond S.M., Teasdale R.D., Liu E.T., Brusic V., Quackenbush J., Wahlestedt C., Mattick J.S., Hume D.A., Kai C., Sasaki D., Tomaru Y., Fukuda S., Kanamori-Katayama M., Suzuki M., Aoki J., Arakawa T., Iida J., Imamura K., Itoh M., Kato T., Kawaji H., Kawagashira N., Kawashima T., Kojima M., Kondo S., Konno H., Nakano K., Ninomiya N., Nishio T., Okada M., Plessy C., Shibata K., Shiraki T., Suzuki S., Tagami M., Waki K., Watahiki A., Okamura-Oho Y., Suzuki H., Kawai J., Hayashizaki Y.
    Science 309:1559-1563(2005) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA].
    Strain: C57BL/6J.
  2. Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    Strain: C57BL/6J.
  3. Mural R.J., Adams M.D., Myers E.W., Smith H.O., Venter J.C.
    Submitted (JUL-2005) to the EMBL/GenBank/DDBJ databases
    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].
    Strain: Czech II.
    Tissue: Mammary tumor.
  5. "Regulation of elongation factor 2 kinase by p90(RSK1) and p70 S6 kinase."
    Wang X., Li W., Williams M., Terada N., Alessi D.R., Proud C.G.
    EMBO J. 20:4370-4379(2001) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION IN PHOSPHORYLATION OF EEF2K.
  6. "p70S6 kinase signals cell survival as well as growth, inactivating the pro-apoptotic molecule BAD."
    Harada H., Andersen J.S., Mann M., Terada N., Korsmeyer S.J.
    Proc. Natl. Acad. Sci. U.S.A. 98:9666-9670(2001) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION IN PHOSPHORYLATION OF BAD, FUNCTION IN APOPTOSIS REGULATION, SUBCELLULAR LOCATION.
  7. "S6K1(-/-)/S6K2(-/-) mice exhibit perinatal lethality and rapamycin-sensitive 5'-terminal oligopyrimidine mRNA translation and reveal a mitogen-activated protein kinase-dependent S6 kinase pathway."
    Pende M., Um S.H., Mieulet V., Sticker M., Goss V.L., Mestan J., Mueller M., Fumagalli S., Kozma S.C., Thomas G.
    Mol. Cell. Biol. 24:3112-3124(2004) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION, DISRUPTION PHENOTYPE.
  8. "S6K directly phosphorylates IRS-1 on Ser-270 to promote insulin resistance in response to TNF-(alpha) signaling through IKK2."
    Zhang J., Gao Z., Yin J., Quon M.J., Ye J.
    J. Biol. Chem. 283:35375-35382(2008) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION IN PHOSPHORYLATION OF IRS1.

Entry informationi

Entry nameiKS6B1_MOUSE
AccessioniPrimary (citable) accession number: Q8BSK8
Secondary accession number(s): Q5SWG1, Q8CHX0
Entry historyi
Integrated into UniProtKB/Swiss-Prot: October 11, 2004
Last sequence update: July 27, 2011
Last modified: July 22, 2015
This is version 125 of the entry and version 2 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programChordata Protein Annotation Program

Miscellaneousi

Keywords - Technical termi

Complete proteome, Reference proteome

Documents

  1. MGD cross-references
    Mouse Genome Database (MGD) cross-references in UniProtKB/Swiss-Prot
  2. Human and mouse protein kinases
    Human and mouse protein kinases: classification and index
  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.