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Protein

Carnitine O-palmitoyltransferase 1, liver isoform

Gene

CPT1A

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

Functioni

Catalyzes the transfer of the acyl group of long-chain fatty acid-CoA conjugates onto carnitine, an essential step for the mitochondrial uptake of long-chain fatty acids and their subsequent beta-oxidation in the mitochondrion. Plays an important role in triglyceride metabolism.

Catalytic activityi

Palmitoyl-CoA + L-carnitine = CoA + L-palmitoylcarnitine.2 Publications

Enzyme regulationi

Inhibited by malonyl-CoA.1 Publication

Pathwayi: fatty acid beta-oxidation

This protein is involved in the pathway fatty acid beta-oxidation, which is part of Lipid metabolism.
View all proteins of this organism that are known to be involved in the pathway fatty acid beta-oxidation and in Lipid metabolism.

Sites

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Active sitei473Proton acceptorBy similarity1
Binding sitei589CarnitineBy similarity1
Binding sitei602CarnitineBy similarity1

GO - Molecular functioni

  • carnitine O-palmitoyltransferase activity Source: UniProtKB
  • palmitoleoyltransferase activity Source: Ensembl

GO - Biological processi

Complete GO annotation...

Keywords - Molecular functioni

Acyltransferase, Transferase

Keywords - Biological processi

Fatty acid metabolism, Lipid metabolism, Transport

Enzyme and pathway databases

BioCyciMetaCyc:HS03286-MONOMER.
ZFISH:HS03286-MONOMER.
BRENDAi2.3.1.21. 2681.
ReactomeiR-HSA-1368082. RORA activates gene expression.
R-HSA-1989781. PPARA activates gene expression.
R-HSA-200425. Import of palmitoyl-CoA into the mitochondrial matrix.
R-HSA-5362517. Signaling by Retinoic Acid.
SABIO-RKP50416.
UniPathwayiUPA00659.

Chemistry databases

SwissLipidsiSLP:000001056.

Names & Taxonomyi

Protein namesi
Recommended name:
Carnitine O-palmitoyltransferase 1, liver isoform (EC:2.3.1.21)
Short name:
CPT1-L
Alternative name(s):
Carnitine O-palmitoyltransferase I, liver isoform
Short name:
CPT I
Short name:
CPTI-L
Carnitine palmitoyltransferase 1A
Gene namesi
Name:CPT1A
Synonyms:CPT1
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
Proteomesi
  • UP000005640 Componenti: Chromosome 11

Organism-specific databases

HGNCiHGNC:2328. CPT1A.

Subcellular locationi

Topology

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Topological domaini2 – 47CytoplasmicSequence analysisAdd BLAST46
Transmembranei48 – 73HelicalSequence analysisAdd BLAST26
Topological domaini74 – 102Mitochondrial intermembraneSequence analysisAdd BLAST29
Transmembranei103 – 122HelicalSequence analysisAdd BLAST20
Topological domaini123 – 773CytoplasmicSequence analysisAdd BLAST651

GO - Cellular componenti

  • integral component of mitochondrial outer membrane Source: UniProtKB
  • membrane Source: UniProtKB
  • mitochondrial inner membrane Source: Ensembl
  • mitochondrial outer membrane Source: Reactome
  • mitochondrion Source: UniProtKB
Complete GO annotation...

Keywords - Cellular componenti

Membrane, Mitochondrion, Mitochondrion outer membrane

Pathology & Biotechi

Involvement in diseasei

Carnitine palmitoyltransferase 1A deficiency (CPT1AD)7 Publications
The disease is caused by mutations affecting the gene represented in this entry.
Disease descriptionRare autosomal recessive metabolic disorder of long-chain fatty acid oxidation characterized by severe episodes of hypoketotic hypoglycemia usually occurring after fasting or illness. Onset is in infancy or early childhood.
See also OMIM:255120
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Natural variantiVAR_020546123R → C in CPT1AD. 1 PublicationCorresponds to variant rs80356775dbSNPEnsembl.1
Natural variantiVAR_020548304C → W in CPT1AD. 1 PublicationCorresponds to variant rs80356789dbSNPEnsembl.1
Natural variantiVAR_020549314T → I in CPT1AD. 1 PublicationCorresponds to variant rs80356776dbSNPEnsembl.1
Natural variantiVAR_046767316R → G in CPT1AD. 1 PublicationCorresponds to variant rs80356796dbSNPEnsembl.1
Natural variantiVAR_046768343F → V in CPT1AD. 1 PublicationCorresponds to variant rs80356783dbSNPEnsembl.1
Natural variantiVAR_020550357R → W in CPT1AD; decreased stability. 1 PublicationCorresponds to variant rs80356777dbSNPEnsembl.1
Natural variantiVAR_020551360E → G in CPT1AD; reduced protein levels. 1 PublicationCorresponds to variant rs28936372dbSNPEnsembl.1
Natural variantiVAR_020552395Missing in CPT1AD; loss of activity. 1 Publication1
Natural variantiVAR_020553414A → V in CPT1AD; decreased activity. 2 PublicationsCorresponds to variant rs28936373dbSNPEnsembl.1
Natural variantiVAR_020554454D → G in CPT1AD. 1 PublicationCorresponds to variant rs80356778dbSNPEnsembl.1
Natural variantiVAR_046769465G → W in CPT1AD. 1 PublicationCorresponds to variant rs80356784dbSNPEnsembl.1
Natural variantiVAR_020555479P → L in CPT1AD; decreased activity. 1 PublicationCorresponds to variant rs80356779dbSNPEnsembl.1
Natural variantiVAR_020556484L → P in CPT1AD. 1 PublicationCorresponds to variant rs80356793dbSNPEnsembl.1
Natural variantiVAR_020557498Y → C in CPT1AD; decreased activity. 2 PublicationsCorresponds to variant rs80356791dbSNPEnsembl.1
Natural variantiVAR_020558709G → E in CPT1AD; loss of activity. 1 PublicationCorresponds to variant rs28936374dbSNPEnsembl.1
Natural variantiVAR_020559710G → E in CPT1AD; loss of activity. 2 PublicationsCorresponds to variant rs80356780dbSNPEnsembl.1

Keywords - Diseasei

Disease mutation

Organism-specific databases

DisGeNETi1374.
MalaCardsiCPT1A.
MIMi255120. phenotype.
OpenTargetsiENSG00000110090.
Orphaneti156. Carnitine palmitoyl transferase 1A deficiency.
PharmGKBiPA26847.

Chemistry databases

ChEMBLiCHEMBL1293194.
DrugBankiDB01016. Glyburide.
DB00583. L-Carnitine.
DB01074. Perhexiline.

Polymorphism and mutation databases

BioMutaiCPT1A.
DMDMi56405343.

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Initiator methionineiRemovedBy similarity
ChainiPRO_00002101592 – 773Carnitine O-palmitoyltransferase 1, liver isoformAdd BLAST772

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Modified residuei2N-acetylalanineBy similarity1
Modified residuei282Nitrated tyrosineBy similarity1
Modified residuei588PhosphothreonineBy similarity1
Modified residuei589Nitrated tyrosineBy similarity1
Modified residuei604PhosphothreonineBy similarity1
Modified residuei741PhosphoserineBy similarity1
Modified residuei747PhosphoserineBy similarity1

Keywords - PTMi

Acetylation, Nitration, Phosphoprotein

Proteomic databases

EPDiP50416.
MaxQBiP50416.
PaxDbiP50416.
PeptideAtlasiP50416.
PRIDEiP50416.

PTM databases

iPTMnetiP50416.
PhosphoSitePlusiP50416.
SwissPalmiP50416.

Expressioni

Tissue specificityi

Strong expression in kidney and heart, and lower in liver and skeletal muscle.

Inductioni

Up-regulated by fatty acids.1 Publication

Gene expression databases

BgeeiENSG00000110090.
CleanExiHS_CPT1A.
ExpressionAtlasiP50416. baseline and differential.
GenevisibleiP50416. HS.

Organism-specific databases

HPAiHPA008835.

Interactioni

Subunit structurei

Homohexamer and homotrimer. Identified in a complex that contains at least CPT1A, ACSL1 and VDAC1. Also identified in complexes with ACSL1 and VDAC2 and VDAC3 (By similarity).By similarity

Protein-protein interaction databases

BioGridi107765. 43 interactors.
IntActiP50416. 27 interactors.
MINTiMINT-3018357.
STRINGi9606.ENSP00000265641.

Chemistry databases

BindingDBiP50416.

Structurei

Secondary structure

1773
Legend: HelixTurnBeta strandPDB Structure known for this area
Show more details
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Helixi4 – 7Combined sources4
Beta strandi9 – 15Combined sources7
Beta strandi18 – 23Combined sources6
Helixi25 – 39Combined sources15

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
2LE3NMR-A1-42[»]
ProteinModelPortaliP50416.
SMRiP50416.
ModBaseiSearch...
MobiDBiSearch...

Family & Domainsi

Region

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Regioni555 – 567Coenzyme A bindingBy similarityAdd BLAST13

Domaini

A conformation change in the N-terminal region spanning the first 42 residues plays an important role in the regulation of enzyme activity by malonyl-CoA.1 Publication

Sequence similaritiesi

Keywords - Domaini

Transmembrane, Transmembrane helix

Phylogenomic databases

eggNOGiKOG3717. Eukaryota.
ENOG410XNZ9. LUCA.
GeneTreeiENSGT00760000119220.
HOGENOMiHOG000233542.
HOVERGENiHBG003458.
InParanoidiP50416.
KOiK08765.
OMAiHIVVFHK.
OrthoDBiEOG091G026C.
PhylomeDBiP50416.
TreeFamiTF313836.

Family and domain databases

InterProiIPR000542. Carn_acyl_trans.
IPR032476. CPT_N.
[Graphical view]
PANTHERiPTHR22589. PTHR22589. 1 hit.
PfamiPF00755. Carn_acyltransf. 1 hit.
PF16484. CPT_N. 1 hit.
[Graphical view]
PROSITEiPS00439. ACYLTRANSF_C_1. 1 hit.
PS00440. ACYLTRANSF_C_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

Isoform 1 (identifier: P50416-1) [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
MAEAHQAVAF QFTVTPDGID LRLSHEALRQ IYLSGLHSWK KKFIRFKNGI
60 70 80 90 100
ITGVYPASPS SWLIVVVGVM TTMYAKIDPS LGIIAKINRT LETANCMSSQ
110 120 130 140 150
TKNVVSGVLF GTGLWVALIV TMRYSLKVLL SYHGWMFTEH GKMSRATKIW
160 170 180 190 200
MGMVKIFSGR KPMLYSFQTS LPRLPVPAVK DTVNRYLQSV RPLMKEEDFK
210 220 230 240 250
RMTALAQDFA VGLGPRLQWY LKLKSWWATN YVSDWWEEYI YLRGRGPLMV
260 270 280 290 300
NSNYYAMDLL YILPTHIQAA RAGNAIHAIL LYRRKLDREE IKPIRLLGST
310 320 330 340 350
IPLCSAQWER MFNTSRIPGE ETDTIQHMRD SKHIVVYHRG RYFKVWLYHD
360 370 380 390 400
GRLLKPREME QQMQRILDNT SEPQPGEARL AALTAGDRVP WARCRQAYFG
410 420 430 440 450
RGKNKQSLDA VEKAAFFVTL DETEEGYRSE DPDTSMDSYA KSLLHGRCYD
460 470 480 490 500
RWFDKSFTFV VFKNGKMGLN AEHSWADAPI VAHLWEYVMS IDSLQLGYAE
510 520 530 540 550
DGHCKGDINP NIPYPTRLQW DIPGECQEVI ETSLNTANLL ANDVDFHSFP
560 570 580 590 600
FVAFGKGIIK KCRTSPDAFV QLALQLAHYK DMGKFCLTYE ASMTRLFREG
610 620 630 640 650
RTETVRSCTT ESCDFVRAMV DPAQTVEQRL KLFKLASEKH QHMYRLAMTG
660 670 680 690 700
SGIDRHLFCL YVVSKYLAVE SPFLKEVLSE PWRLSTSQTP QQQVELFDLE
710 720 730 740 750
NNPEYVSSGG GFGPVADDGY GVSYILVGEN LINFHISSKF SCPETDSHRF
760 770
GRHLKEAMTD IITLFGLSSN SKK
Length:773
Mass (Da):88,368
Last modified:December 7, 2004 - v2
Checksum:iE5DC9141B6301947
GO
Isoform 2 (identifier: P50416-2) [UniParc]FASTAAdd to basket

The sequence of this isoform differs from the canonical sequence as follows:
     746-773: DSHRFGRHLKEAMTDIITLFGLSSNSKK → GIISQGPSSDT

Show »
Length:756
Mass (Da):86,239
Checksum:iC7B0ED8A26285110
GO

Experimental Info

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sequence conflicti479P → Q in AAC41748 (PubMed:7892212).Curated1
Sequence conflicti568A → T in AAC41748 (PubMed:7892212).Curated1

Natural variant

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Natural variantiVAR_020546123R → C in CPT1AD. 1 PublicationCorresponds to variant rs80356775dbSNPEnsembl.1
Natural variantiVAR_020547275A → T.3 PublicationsCorresponds to variant rs2229738dbSNPEnsembl.1
Natural variantiVAR_020548304C → W in CPT1AD. 1 PublicationCorresponds to variant rs80356789dbSNPEnsembl.1
Natural variantiVAR_020549314T → I in CPT1AD. 1 PublicationCorresponds to variant rs80356776dbSNPEnsembl.1
Natural variantiVAR_046767316R → G in CPT1AD. 1 PublicationCorresponds to variant rs80356796dbSNPEnsembl.1
Natural variantiVAR_046768343F → V in CPT1AD. 1 PublicationCorresponds to variant rs80356783dbSNPEnsembl.1
Natural variantiVAR_020550357R → W in CPT1AD; decreased stability. 1 PublicationCorresponds to variant rs80356777dbSNPEnsembl.1
Natural variantiVAR_020551360E → G in CPT1AD; reduced protein levels. 1 PublicationCorresponds to variant rs28936372dbSNPEnsembl.1
Natural variantiVAR_020552395Missing in CPT1AD; loss of activity. 1 Publication1
Natural variantiVAR_020553414A → V in CPT1AD; decreased activity. 2 PublicationsCorresponds to variant rs28936373dbSNPEnsembl.1
Natural variantiVAR_020554454D → G in CPT1AD. 1 PublicationCorresponds to variant rs80356778dbSNPEnsembl.1
Natural variantiVAR_046769465G → W in CPT1AD. 1 PublicationCorresponds to variant rs80356784dbSNPEnsembl.1
Natural variantiVAR_020555479P → L in CPT1AD; decreased activity. 1 PublicationCorresponds to variant rs80356779dbSNPEnsembl.1
Natural variantiVAR_020556484L → P in CPT1AD. 1 PublicationCorresponds to variant rs80356793dbSNPEnsembl.1
Natural variantiVAR_020557498Y → C in CPT1AD; decreased activity. 2 PublicationsCorresponds to variant rs80356791dbSNPEnsembl.1
Natural variantiVAR_020558709G → E in CPT1AD; loss of activity. 1 PublicationCorresponds to variant rs28936374dbSNPEnsembl.1
Natural variantiVAR_020559710G → E in CPT1AD; loss of activity. 2 PublicationsCorresponds to variant rs80356780dbSNPEnsembl.1

Alternative sequence

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Alternative sequenceiVSP_012167746 – 773DSHRF…SNSKK → GIISQGPSSDT in isoform 2. 2 PublicationsAdd BLAST28

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
L39211 mRNA. Translation: AAC41748.1.
AJ420747 Genomic DNA. Translation: CAD12625.1.
AJ420748 Genomic DNA. Translation: CAD59673.1.
BT009791 mRNA. Translation: AAP88793.1.
BC000185 mRNA. Translation: AAH00185.1.
CCDSiCCDS31624.1. [P50416-2]
CCDS8185.1. [P50416-1]
PIRiI59351.
RefSeqiNP_001027017.1. NM_001031847.2. [P50416-2]
NP_001867.2. NM_001876.3. [P50416-1]
XP_016872709.1. XM_017017220.1. [P50416-1]
UniGeneiHs.503043.

Genome annotation databases

EnsembliENST00000265641; ENSP00000265641; ENSG00000110090. [P50416-1]
ENST00000376618; ENSP00000365803; ENSG00000110090. [P50416-2]
ENST00000539743; ENSP00000446108; ENSG00000110090. [P50416-1]
ENST00000540367; ENSP00000439084; ENSG00000110090. [P50416-2]
GeneIDi1374.
KEGGihsa:1374.
UCSCiuc001oof.5. human. [P50416-1]

Keywords - Coding sequence diversityi

Alternative splicing, Polymorphism

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
L39211 mRNA. Translation: AAC41748.1.
AJ420747 Genomic DNA. Translation: CAD12625.1.
AJ420748 Genomic DNA. Translation: CAD59673.1.
BT009791 mRNA. Translation: AAP88793.1.
BC000185 mRNA. Translation: AAH00185.1.
CCDSiCCDS31624.1. [P50416-2]
CCDS8185.1. [P50416-1]
PIRiI59351.
RefSeqiNP_001027017.1. NM_001031847.2. [P50416-2]
NP_001867.2. NM_001876.3. [P50416-1]
XP_016872709.1. XM_017017220.1. [P50416-1]
UniGeneiHs.503043.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
2LE3NMR-A1-42[»]
ProteinModelPortaliP50416.
SMRiP50416.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi107765. 43 interactors.
IntActiP50416. 27 interactors.
MINTiMINT-3018357.
STRINGi9606.ENSP00000265641.

Chemistry databases

BindingDBiP50416.
ChEMBLiCHEMBL1293194.
DrugBankiDB01016. Glyburide.
DB00583. L-Carnitine.
DB01074. Perhexiline.
SwissLipidsiSLP:000001056.

PTM databases

iPTMnetiP50416.
PhosphoSitePlusiP50416.
SwissPalmiP50416.

Polymorphism and mutation databases

BioMutaiCPT1A.
DMDMi56405343.

Proteomic databases

EPDiP50416.
MaxQBiP50416.
PaxDbiP50416.
PeptideAtlasiP50416.
PRIDEiP50416.

Protocols and materials databases

DNASUi1374.
Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000265641; ENSP00000265641; ENSG00000110090. [P50416-1]
ENST00000376618; ENSP00000365803; ENSG00000110090. [P50416-2]
ENST00000539743; ENSP00000446108; ENSG00000110090. [P50416-1]
ENST00000540367; ENSP00000439084; ENSG00000110090. [P50416-2]
GeneIDi1374.
KEGGihsa:1374.
UCSCiuc001oof.5. human. [P50416-1]

Organism-specific databases

CTDi1374.
DisGeNETi1374.
GeneCardsiCPT1A.
GeneReviewsiCPT1A.
HGNCiHGNC:2328. CPT1A.
HPAiHPA008835.
MalaCardsiCPT1A.
MIMi255120. phenotype.
600528. gene.
neXtProtiNX_P50416.
OpenTargetsiENSG00000110090.
Orphaneti156. Carnitine palmitoyl transferase 1A deficiency.
PharmGKBiPA26847.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiKOG3717. Eukaryota.
ENOG410XNZ9. LUCA.
GeneTreeiENSGT00760000119220.
HOGENOMiHOG000233542.
HOVERGENiHBG003458.
InParanoidiP50416.
KOiK08765.
OMAiHIVVFHK.
OrthoDBiEOG091G026C.
PhylomeDBiP50416.
TreeFamiTF313836.

Enzyme and pathway databases

UniPathwayiUPA00659.
BioCyciMetaCyc:HS03286-MONOMER.
ZFISH:HS03286-MONOMER.
BRENDAi2.3.1.21. 2681.
ReactomeiR-HSA-1368082. RORA activates gene expression.
R-HSA-1989781. PPARA activates gene expression.
R-HSA-200425. Import of palmitoyl-CoA into the mitochondrial matrix.
R-HSA-5362517. Signaling by Retinoic Acid.
SABIO-RKP50416.

Miscellaneous databases

ChiTaRSiCPT1A. human.
GenomeRNAii1374.
PROiP50416.
SOURCEiSearch...

Gene expression databases

BgeeiENSG00000110090.
CleanExiHS_CPT1A.
ExpressionAtlasiP50416. baseline and differential.
GenevisibleiP50416. HS.

Family and domain databases

InterProiIPR000542. Carn_acyl_trans.
IPR032476. CPT_N.
[Graphical view]
PANTHERiPTHR22589. PTHR22589. 1 hit.
PfamiPF00755. Carn_acyltransf. 1 hit.
PF16484. CPT_N. 1 hit.
[Graphical view]
PROSITEiPS00439. ACYLTRANSF_C_1. 1 hit.
PS00440. ACYLTRANSF_C_2. 1 hit.
[Graphical view]
ProtoNetiSearch...

Entry informationi

Entry nameiCPT1A_HUMAN
AccessioniPrimary (citable) accession number: P50416
Secondary accession number(s): Q8TCU0, Q9BWK0
Entry historyi
Integrated into UniProtKB/Swiss-Prot: October 1, 1996
Last sequence update: December 7, 2004
Last modified: November 2, 2016
This is version 162 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

3D-structure, Complete proteome, Reference proteome

Documents

  1. Human chromosome 11
    Human chromosome 11: 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. PATHWAY comments
    Index of metabolic and biosynthesis pathways
  6. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  7. 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.