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Protein

Actin, cytoplasmic 1

Gene

Actb

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

Functioni

Actins are highly conserved proteins that are involved in various types of cell motility and are ubiquitously expressed in all eukaryotic cells.

GO - Molecular functioni

GO - Biological processi

Complete GO annotation...

Keywords - Ligandi

ATP-binding, Nucleotide-binding

Enzyme and pathway databases

ReactomeiREACT_272375. Folding of actin by CCT/TriC.
REACT_280010. Factors involved in megakaryocyte development and platelet production.
REACT_280776. Gap junction degradation.
REACT_291621. HATs acetylate histones.
REACT_291802. Formation of annular gap junctions.
REACT_298063. Prefoldin mediated transfer of substrate to CCT/TriC.
REACT_302653. Translocation of GLUT4 to the plasma membrane.
REACT_308832. Adherens junctions interactions.
REACT_313804. EPHB-mediated forward signaling.
REACT_315885. VEGFA-VEGFR2 Pathway.
REACT_318927. Interaction between L1 and Ankyrins.
REACT_320343. Cell-extracellular matrix interactions.
REACT_344463. Regulation of actin dynamics for phagocytic cup formation.
REACT_353475. Recycling pathway of L1.
REACT_358203. RHO GTPases activate IQGAPs.
REACT_358264. RHO GTPases Activate Formins.
REACT_358608. RHO GTPases Activate WASPs and WAVEs.

Names & Taxonomyi

Protein namesi
Recommended name:
Actin, cytoplasmic 1
Alternative name(s):
Beta-actin
Cleaved into the following chain:
Gene namesi
Name:Actb
OrganismiMus musculus (Mouse)
Taxonomic identifieri10090 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresGliresRodentiaSciurognathiMuroideaMuridaeMurinaeMusMus
ProteomesiUP000000589 Componenti: Chromosome 5

Organism-specific databases

MGIiMGI:87904. Actb.

Subcellular locationi

  • Cytoplasmcytoskeleton

  • Note: Localized in cytoplasmic mRNP granules containing untranslated mRNAs.By similarity

GO - Cellular componenti

Complete GO annotation...

Keywords - Cellular componenti

Cytoplasm, Cytoskeleton

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Chaini1 – 375375Actin, cytoplasmic 1PRO_0000367076Add
BLAST
Initiator methioninei1 – 11Removed; alternate1 Publication
Chaini2 – 375374Actin, cytoplasmic 1, N-terminally processedPRO_0000000775Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei1 – 11N-acetylmethionineBy similarity
Modified residuei2 – 21N-acetylaspartate; in Actin, cytoplasmic 1, N-terminally processed1 Publication
Modified residuei44 – 441Methionine (R)-sulfoxide1 Publication
Modified residuei47 – 471Methionine (R)-sulfoxide1 Publication
Modified residuei73 – 731Tele-methylhistidine1 Publication
Modified residuei84 – 841N6-methyllysineBy similarity

Post-translational modificationi

ISGylated.1 Publication
Oxidation of Met-44 and Met-47 by MICALs (MICAL1, MICAL2 or MICAL3) to form methionine sulfoxide promotes actin filament depolymerization. MICAL1 and MICAL2 produce the (R)-S-oxide form. The (R)-S-oxide form is reverted by MSRB1 and MSRB2, which promote actin repolymerization.1 Publication
Monomethylation at Lys-84 (K84me1) regulates actin-myosin interaction and actomyosin-dependent processes. Demethylation by ALKBH4 is required for maintaining actomyosin dynamics supporting normal cleavage furrow ingression during cytokinesis and cell migration (By similarity).By similarity

Keywords - PTMi

Acetylation, Methylation, Oxidation, Ubl conjugation

Proteomic databases

MaxQBiP60710.
PRIDEiP60710.

2D gel databases

COMPLUYEAST-2DPAGEP60710.
REPRODUCTION-2DPAGEP60710.
SWISS-2DPAGEP99041.
UCD-2DPAGEP60710.

PTM databases

PhosphoSiteiP60710.

Expressioni

Gene expression databases

BgeeiP60710.
CleanExiMM_ACTB.
ExpressionAtlasiP60710. baseline and differential.
GenevisibleiP60710. MM.

Interactioni

Subunit structurei

Polymerization of globular actin (G-actin) leads to a structural filament (F-actin) in the form of a two-stranded helix. Each actin can bind to 4 others. Identified in a IGF2BP1-dependent mRNP granule complex containing untranslated mRNAs. Component of the BAF complex, which includes at least actin (ACTB), ARID1A, ARID1B/BAF250, SMARCA2, SMARCA4/BRG1, MARCB1/BAF47, ACTL6A/BAF53, ACTL6B/BAF53B, SMARCE1/BAF57, SMARCC1/BAF155, SMARCC2/BAF170, SMARCB1/SNF5/INI1, and one or more of SMARCD1/BAF60A, SMARCD2/BAF60B, or SMARCD3/BAF60C. In muscle cells, the BAF complex also contains DPF3. Found in a complex with XPO6, Ran, ACTB and PFN1. Component of a complex composed at least of ACTB, AP2M1, AP2A1, AP2A2, MEGF10 and VIM. Component of the MLL5-L complex, at least composed of KMT2E/MLL5, STK38, PPP1CA, PPP1CB, PPP1CC, HCFC1, ACTB and OGT. Interacts with XPO6 and EMD. Interacts with ERBB2. Interacts with GCSAM (By similarity).By similarity

Binary interactionsi

WithEntry#Exp.IntActNotes
CxadrP977926EBI-353957,EBI-7429264

Protein-protein interaction databases

BioGridi197944. 30 interactions.
DIPiDIP-31574N.
IntActiP60710. 43 interactions.
MINTiMINT-1202772.

Structurei

3D structure databases

ProteinModelPortaliP60710.
SMRiP60710. Positions 6-375.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Sequence similaritiesi

Belongs to the actin family.Curated

Phylogenomic databases

GeneTreeiENSGT00760000118957.
HOVERGENiHBG003771.
InParanoidiP60710.
KOiK05692.
OMAiASMLQMW.
OrthoDBiEOG72RMZ1.
PhylomeDBiP60710.
TreeFamiTF354237.

Family and domain databases

InterProiIPR004000. Actin.
IPR020902. Actin/actin-like_CS.
IPR004001. Actin_CS.
[Graphical view]
PANTHERiPTHR11937. PTHR11937. 1 hit.
PfamiPF00022. Actin. 1 hit.
[Graphical view]
PRINTSiPR00190. ACTIN.
SMARTiSM00268. ACTIN. 1 hit.
[Graphical view]
PROSITEiPS00406. ACTINS_1. 1 hit.
PS00432. ACTINS_2. 1 hit.
PS01132. ACTINS_ACT_LIKE. 1 hit.
[Graphical view]

Sequencei

Sequence statusi: Complete.

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

P60710-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MDDDIAALVV DNGSGMCKAG FAGDDAPRAV FPSIVGRPRH QGVMVGMGQK
60 70 80 90 100
DSYVGDEAQS KRGILTLKYP IEHGIVTNWD DMEKIWHHTF YNELRVAPEE
110 120 130 140 150
HPVLLTEAPL NPKANREKMT QIMFETFNTP AMYVAIQAVL SLYASGRTTG
160 170 180 190 200
IVMDSGDGVT HTVPIYEGYA LPHAILRLDL AGRDLTDYLM KILTERGYSF
210 220 230 240 250
TTTAEREIVR DIKEKLCYVA LDFEQEMATA ASSSSLEKSY ELPDGQVITI
260 270 280 290 300
GNERFRCPEA LFQPSFLGME SCGIHETTFN SIMKCDVDIR KDLYANTVLS
310 320 330 340 350
GGTTMYPGIA DRMQKEITAL APSTMKIKII APPERKYSVW IGGSILASLS
360 370
TFQQMWISKQ EYDESGPSIV HRKCF
Length:375
Mass (Da):41,737
Last modified:April 1, 1988 - v1
Checksum:i6AFD05CA94E360E2
GO

Experimental Info

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Sequence conflicti38 – 381P → S in CAA27396 (PubMed:3084797).Curated
Sequence conflicti38 – 381P → S in AAA37144 (PubMed:3084797).Curated
Sequence conflicti52 – 521S → F in BAE39957 (PubMed:16141072).Curated
Sequence conflicti80 – 801D → E in BAE35572 (PubMed:16141072).Curated
Sequence conflicti109 – 1091P → T in BAE39957 (PubMed:16141072).Curated
Sequence conflicti156 – 1561G → R in BAE39957 (PubMed:16141072).Curated
Sequence conflicti178 – 1781L → V in BAE39957 (PubMed:16141072).Curated

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
X03672 mRNA. Translation: CAA27307.1.
AK088691 mRNA. Translation: BAC40507.1.
AK145191 mRNA. Translation: BAE26283.1.
AK145196 mRNA. Translation: BAE26288.1.
AK145308 mRNA. Translation: BAE26359.1.
AK150711 mRNA. Translation: BAE29789.1.
AK150879 mRNA. Translation: BAE29928.1.
AK151010 mRNA. Translation: BAE30031.1.
AK151136 mRNA. Translation: BAE30144.1.
AK151145 mRNA. Translation: BAE30152.1.
AK151159 mRNA. Translation: BAE30164.1.
AK151166 mRNA. Translation: BAE30169.1.
AK151190 mRNA. Translation: BAE30187.1.
AK151202 mRNA. Translation: BAE30199.1.
AK151226 mRNA. Translation: BAE30218.1.
AK151277 mRNA. Translation: BAE30264.1.
AK151350 mRNA. Translation: BAE30326.1.
AK151398 mRNA. Translation: BAE30366.1.
AK151995 mRNA. Translation: BAE30859.1.
AK151999 mRNA. Translation: BAE30863.1.
AK152615 mRNA. Translation: BAE31359.1.
AK152651 mRNA. Translation: BAE31388.1.
AK152844 mRNA. Translation: BAE31537.1.
AK159759 mRNA. Translation: BAE35350.1.
AK159834 mRNA. Translation: BAE35412.1.
AK160029 mRNA. Translation: BAE35572.1.
AK166349 mRNA. Translation: BAE38723.1.
AK166498 mRNA. Translation: BAE38810.1.
AK167117 mRNA. Translation: BAE39265.1.
AK167960 mRNA. Translation: BAE39957.1.
X03765 mRNA. Translation: CAA27396.1.
M12481 mRNA. Translation: AAA37144.1.
CCDSiCCDS19833.1.
PIRiA39104. ATMSB.
RefSeqiNP_031419.1. NM_007393.3.
UniGeneiMm.328431.
Mm.391967.
Mm.469717.

Genome annotation databases

EnsembliENSMUST00000100497; ENSMUSP00000098066; ENSMUSG00000029580.
GeneIDi11461.
KEGGimmu:11461.
UCSCiuc009ajk.1. mouse.

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
X03672 mRNA. Translation: CAA27307.1.
AK088691 mRNA. Translation: BAC40507.1.
AK145191 mRNA. Translation: BAE26283.1.
AK145196 mRNA. Translation: BAE26288.1.
AK145308 mRNA. Translation: BAE26359.1.
AK150711 mRNA. Translation: BAE29789.1.
AK150879 mRNA. Translation: BAE29928.1.
AK151010 mRNA. Translation: BAE30031.1.
AK151136 mRNA. Translation: BAE30144.1.
AK151145 mRNA. Translation: BAE30152.1.
AK151159 mRNA. Translation: BAE30164.1.
AK151166 mRNA. Translation: BAE30169.1.
AK151190 mRNA. Translation: BAE30187.1.
AK151202 mRNA. Translation: BAE30199.1.
AK151226 mRNA. Translation: BAE30218.1.
AK151277 mRNA. Translation: BAE30264.1.
AK151350 mRNA. Translation: BAE30326.1.
AK151398 mRNA. Translation: BAE30366.1.
AK151995 mRNA. Translation: BAE30859.1.
AK151999 mRNA. Translation: BAE30863.1.
AK152615 mRNA. Translation: BAE31359.1.
AK152651 mRNA. Translation: BAE31388.1.
AK152844 mRNA. Translation: BAE31537.1.
AK159759 mRNA. Translation: BAE35350.1.
AK159834 mRNA. Translation: BAE35412.1.
AK160029 mRNA. Translation: BAE35572.1.
AK166349 mRNA. Translation: BAE38723.1.
AK166498 mRNA. Translation: BAE38810.1.
AK167117 mRNA. Translation: BAE39265.1.
AK167960 mRNA. Translation: BAE39957.1.
X03765 mRNA. Translation: CAA27396.1.
M12481 mRNA. Translation: AAA37144.1.
CCDSiCCDS19833.1.
PIRiA39104. ATMSB.
RefSeqiNP_031419.1. NM_007393.3.
UniGeneiMm.328431.
Mm.391967.
Mm.469717.

3D structure databases

ProteinModelPortaliP60710.
SMRiP60710. Positions 6-375.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi197944. 30 interactions.
DIPiDIP-31574N.
IntActiP60710. 43 interactions.
MINTiMINT-1202772.

PTM databases

PhosphoSiteiP60710.

2D gel databases

COMPLUYEAST-2DPAGEP60710.
REPRODUCTION-2DPAGEP60710.
SWISS-2DPAGEP99041.
UCD-2DPAGEP60710.

Proteomic databases

MaxQBiP60710.
PRIDEiP60710.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENSMUST00000100497; ENSMUSP00000098066; ENSMUSG00000029580.
GeneIDi11461.
KEGGimmu:11461.
UCSCiuc009ajk.1. mouse.

Organism-specific databases

CTDi60.
MGIiMGI:87904. Actb.

Phylogenomic databases

GeneTreeiENSGT00760000118957.
HOVERGENiHBG003771.
InParanoidiP60710.
KOiK05692.
OMAiASMLQMW.
OrthoDBiEOG72RMZ1.
PhylomeDBiP60710.
TreeFamiTF354237.

Enzyme and pathway databases

ReactomeiREACT_272375. Folding of actin by CCT/TriC.
REACT_280010. Factors involved in megakaryocyte development and platelet production.
REACT_280776. Gap junction degradation.
REACT_291621. HATs acetylate histones.
REACT_291802. Formation of annular gap junctions.
REACT_298063. Prefoldin mediated transfer of substrate to CCT/TriC.
REACT_302653. Translocation of GLUT4 to the plasma membrane.
REACT_308832. Adherens junctions interactions.
REACT_313804. EPHB-mediated forward signaling.
REACT_315885. VEGFA-VEGFR2 Pathway.
REACT_318927. Interaction between L1 and Ankyrins.
REACT_320343. Cell-extracellular matrix interactions.
REACT_344463. Regulation of actin dynamics for phagocytic cup formation.
REACT_353475. Recycling pathway of L1.
REACT_358203. RHO GTPases activate IQGAPs.
REACT_358264. RHO GTPases Activate Formins.
REACT_358608. RHO GTPases Activate WASPs and WAVEs.

Miscellaneous databases

ChiTaRSiActb. mouse.
NextBioi278784.
PROiP60710.
SOURCEiSearch...

Gene expression databases

BgeeiP60710.
CleanExiMM_ACTB.
ExpressionAtlasiP60710. baseline and differential.
GenevisibleiP60710. MM.

Family and domain databases

InterProiIPR004000. Actin.
IPR020902. Actin/actin-like_CS.
IPR004001. Actin_CS.
[Graphical view]
PANTHERiPTHR11937. PTHR11937. 1 hit.
PfamiPF00022. Actin. 1 hit.
[Graphical view]
PRINTSiPR00190. ACTIN.
SMARTiSM00268. ACTIN. 1 hit.
[Graphical view]
PROSITEiPS00406. ACTINS_1. 1 hit.
PS00432. ACTINS_2. 1 hit.
PS01132. ACTINS_ACT_LIKE. 1 hit.
[Graphical view]
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "Nucleotide sequence of a full-length cDNA for mouse cytoskeletal beta-actin mRNA."
    Tokunaga K., Taniguchi H., Yoda K., Shimizu M., Sakiyama S.
    Nucleic Acids Res. 14:2829-2829(1986) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA].
  2. "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: BALB/c, C57BL/6J and NOD.
    Tissue: Bone marrow, Mammary gland and Thymus.
  3. "Actin amino-acid sequences. Comparison of actins from calf thymus, bovine brain, and SV40-transformed mouse 3T3 cells with rabbit skeletal muscle actin."
    Vandekerckhove J., Weber K.
    Eur. J. Biochem. 90:451-462(1978) [PubMed] [Europe PMC] [Abstract]
    Cited for: PROTEIN SEQUENCE OF 2-375, CLEAVAGE OF INITIATOR METHIONINE, ACETYLATION AT ASP-2, METHYLATION AT HIS-73.
    Tissue: Thymus.
  4. Lubec G., Klug S., Kang S.U., Sunyer B., Chen W.-Q.
    Submitted (JAN-2009) to UniProtKB
    Cited for: PROTEIN SEQUENCE OF 19-39; 51-61; 85-113; 148-177; 184-191; 197-206; 216-254; 257-284; 291-326 AND 360-372, IDENTIFICATION BY MASS SPECTROMETRY.
    Strain: C57BL/6 and OF1.
    Tissue: Brain and Hippocampus.
  5. "Comparison of three actin-coding sequences in the mouse; evolutionary relationships between the actin genes of warm-blooded vertebrates."
    Alonso S., Minty A., Bourlet Y., Buckingham M.
    J. Mol. Evol. 23:11-22(1986) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [MRNA] OF 27-375.
  6. Vilbois F.
    Submitted (OCT-1998) to UniProtKB
    Cited for: ACETYLATION.
    Tissue: Muscle.
  7. Cited for: ISGYLATION.
  8. "MsrB1 and MICALs regulate actin assembly and macrophage function via reversible stereoselective methionine oxidation."
    Lee B.C., Peterfi Z., Hoffmann F.W., Moore R.E., Kaya A., Avanesov A., Tarrago L., Zhou Y., Weerapana E., Fomenko D.E., Hoffmann P.R., Gladyshev V.N.
    Mol. Cell 51:397-404(2013) [PubMed] [Europe PMC] [Abstract]
    Cited for: OXIDATION AT MET-44 AND MET-47, DEOXIDATION AT MET-44 AND MET-47.

Entry informationi

Entry nameiACTB_MOUSE
AccessioniPrimary (citable) accession number: P60710
Secondary accession number(s): P02570
, P70514, P99021, Q11211, Q3TI89, Q3TVP6, Q64316, Q6ZWM3
Entry historyi
Integrated into UniProtKB/Swiss-Prot: July 21, 1986
Last sequence update: April 1, 1988
Last modified: June 24, 2015
This is version 123 of the entry and version 1 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programChordata Protein Annotation Program

Miscellaneousi

Miscellaneous

In vertebrates 3 main groups of actin isoforms, alpha, beta and gamma have been identified. The alpha actins are found in muscle tissues and are a major constituent of the contractile apparatus. The beta and gamma actins coexist in most cell types as components of the cytoskeleton and as mediators of internal cell motility.

Keywords - Technical termi

Complete proteome, Direct protein sequencing, Reference proteome

Documents

  1. MGD cross-references
    Mouse Genome Database (MGD) cross-references in UniProtKB/Swiss-Prot
  2. 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.