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Protein

Hemoglobin subunit gamma-2

Gene

HBG2

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

Functioni

Gamma chains make up the fetal hemoglobin F, in combination with alpha chains.

Sites

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Metal bindingi64 – 641Iron (heme distal ligand)By similarity
Metal bindingi93 – 931Iron (heme proximal ligand)Combined sources1 Publication

GO - Molecular functioni

GO - Biological processi

Complete GO annotation...

Keywords - Biological processi

Oxygen transport, Transport

Keywords - Ligandi

Heme, Iron, Metal-binding

Enzyme and pathway databases

ReactomeiR-HSA-983231. Factors involved in megakaryocyte development and platelet production.

Names & Taxonomyi

Protein namesi
Recommended name:
Hemoglobin subunit gamma-2
Alternative name(s):
Gamma-2-globin
Hb F Ggamma
Hemoglobin gamma-2 chain
Hemoglobin gamma-G chain
Gene namesi
Name:HBG2
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
Proteomesi
  • UP000005640 Componenti: Chromosome 11

Organism-specific databases

HGNCiHGNC:4832. HBG2.

Subcellular locationi

GO - Cellular componenti

  • blood microparticle Source: UniProtKB
  • cytosol Source: Reactome
  • hemoglobin complex Source: InterPro
Complete GO annotation...

Pathology & Biotechi

Involvement in diseasei

Cyanosis transient neonatal (TNCY)6 Publications
The disease is caused by mutations affecting the gene represented in this entry.
Disease descriptionA disorder characterized by cyanosis in the fetus and neonate, due to a defect in the fetal hemoglobin chain which has reduced affinity for oxygen. Some patients develop anemia resulting from increased destruction of red cells containing abnormal or unstable hemoglobin. The cyanosis resolves spontaneously by 5 to 6 months of age or earlier, as the adult beta-globin chain is produced and replaces the fetal gamma-globin chain.
See also OMIM:613977
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Natural varianti42 – 421F → S in TNCY; hemoglobin Cincinnati. 1 Publication
Corresponds to variant rs34878913 [ dbSNP | Ensembl ].
VAR_003146
Natural varianti64 – 641H → L in TNCY; hemoglobin M-Circleville. 2 Publications
VAR_025336
Natural varianti64 – 641H → Y in TNCY; hemoglobin Osaka; the presence of a tyrosine causes the formation of a covalent link with heme iron, so that the iron is stabilized in the ferric form; when this occurs methemoglobin is formed, oxygen can no longer bind to heme and cyanosis occurs. 2 Publications
Corresponds to variant rs34474104 [ dbSNP | Ensembl ].
VAR_003154
Natural varianti68 – 681V → M in TNCY; hemoglobin Toms River; the side chain of methionine decreases both the affinity of oxygen for binding to the mutant hemoglobin subunit via steric hindrance and the rate at which it does so; the mutant methionine is converted to aspartic acid post-translationally. 1 Publication
Corresponds to variant rs587776864 [ dbSNP | Ensembl ].
VAR_065950
Natural varianti93 – 931H → Y in TNCY; hemoglobin Fort Ripley. 1 Publication
Corresponds to variant rs35103459 [ dbSNP | Ensembl ].
VAR_003166
Natural varianti106 – 1061L → H in TNCY; hemoglobin F-Brugine/Feldkirch; lowered affinity for oxygen. 1 Publication
VAR_073159

Keywords - Diseasei

Disease mutation

Organism-specific databases

MalaCardsiHBG2.
MIMi613977. phenotype.
Orphaneti280615. Hemoglobinopathy Toms River.
46532. Hereditary persistence of fetal hemoglobin - beta-thalassemia.
251380. Hereditary persistence of fetal hemoglobin - sickle cell disease.
PharmGKBiPA29207.

Polymorphism and mutation databases

BioMutaiHBG2.
DMDMi56749861.

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Initiator methionineiRemoved3 Publications
Chaini2 – 147146Hemoglobin subunit gamma-2PRO_0000053254Add
BLAST

Amino acid modifications

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Modified residuei2 – 21N-acetylglycine; in form Hb F11 Publication
Modified residuei45 – 451PhosphoserineCombined sources
Modified residuei51 – 511PhosphoserineCombined sources
Modified residuei53 – 531PhosphoserineCombined sources
Modified residuei140 – 1401PhosphoserineCombined sources
Modified residuei143 – 1431PhosphoserineCombined sources
Modified residuei144 – 1441PhosphoserineCombined sources

Post-translational modificationi

Acetylation of Gly-2 converts Hb F to the minor Hb F1.1 Publication

Keywords - PTMi

Acetylation, Phosphoprotein

Proteomic databases

EPDiP69892.
MaxQBiP69892.
PaxDbiP69892.
PeptideAtlasiP69892.
PRIDEiP69892.

PTM databases

iPTMnetiP69892.
PhosphoSiteiP69892.

Expressioni

Tissue specificityi

Red blood cells.

Developmental stagei

Expressed until four or five weeks after birth.

Gene expression databases

BgeeiENSG00000196565.
CleanExiHS_HBG2.
ExpressionAtlasiP69892. baseline and differential.
GenevisibleiP69892. HS.

Organism-specific databases

HPAiCAB016143.
HPA043234.

Interactioni

Subunit structurei

Heterotetramer of two alpha chains and two gamma chains in fetal hemoglobin (Hb F).1 Publication

Protein-protein interaction databases

BioGridi109298. 8 interactions.
IntActiP69892. 6 interactions.
MINTiMINT-1200269.
STRINGi9606.ENSP00000338082.

Structurei

Secondary structure

1
147
Legend: HelixTurnBeta strand
Show more details
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Helixi6 – 1813Combined sources
Helixi21 – 3515Combined sources
Helixi37 – 426Combined sources
Helixi44 – 463Combined sources
Helixi52 – 565Combined sources
Helixi59 – 7618Combined sources
Helixi77 – 815Combined sources
Helixi82 – 854Combined sources
Helixi87 – 959Combined sources
Helixi102 – 11918Combined sources
Helixi120 – 1223Combined sources
Helixi125 – 14218Combined sources
Helixi143 – 1464Combined sources

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
1FDHX-ray2.50G/H2-147[»]
4MQJX-ray1.80B/D/F/H3-147[»]
4MQKX-ray2.24B/D/F/H2-147[»]
ProteinModelPortaliP69892.
SMRiP69892. Positions 3-147.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiP69892.

Family & Domainsi

Sequence similaritiesi

Belongs to the globin family.PROSITE-ProRule annotation

Phylogenomic databases

eggNOGiKOG3378. Eukaryota.
COG1018. LUCA.
GeneTreeiENSGT00760000119197.
HOVERGENiHBG009709.
InParanoidiP69892.
KOiK13824.
PhylomeDBiP69892.
TreeFamiTF333268.

Family and domain databases

CDDicd08925. Hb-beta_like. 1 hit.
Gene3Di1.10.490.10. 1 hit.
InterProiIPR000971. Globin.
IPR009050. Globin-like.
IPR012292. Globin/Proto.
IPR002337. Haemoglobin_b.
[Graphical view]
PfamiPF00042. Globin. 1 hit.
[Graphical view]
PRINTSiPR00814. BETAHAEM.
SUPFAMiSSF46458. SSF46458. 1 hit.
PROSITEiPS01033. GLOBIN. 1 hit.
[Graphical view]

Sequencei

Sequence statusi: Complete.

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

P69892-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MGHFTEEDKA TITSLWGKVN VEDAGGETLG RLLVVYPWTQ RFFDSFGNLS
60 70 80 90 100
SASAIMGNPK VKAHGKKVLT SLGDAIKHLD DLKGTFAQLS ELHCDKLHVD
110 120 130 140
PENFKLLGNV LVTVLAIHFG KEFTPEVQAS WQKMVTGVAS ALSSRYH
Length:147
Mass (Da):16,126
Last modified:January 23, 2007 - v2
Checksum:i8FCDC4441B416DDE
GO

Sequence cautioni

The sequence AAB50159 differs from that shown. Reason: Erroneous initiation. Translation N-terminally shortened.Curated

Natural variant

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Natural varianti2 – 21G → C in Malaysia. 1 Publication
Corresponds to variant rs36006195 [ dbSNP | Ensembl ].
VAR_003123
Natural varianti6 – 61E → G in Meinohama. 1 Publication
Corresponds to variant rs34263826 [ dbSNP | Ensembl ].
VAR_003126
Natural varianti8 – 81D → N in Auckland. 1 Publication
Corresponds to variant rs34501593 [ dbSNP | Ensembl ].
VAR_003129
Natural varianti9 – 91K → E in Albaicin. 1 Publication
Corresponds to variant rs35521813 [ dbSNP | Ensembl ].
VAR_020643
Natural varianti9 – 91K → Q in Albaicin. 1 Publication
Corresponds to variant rs35521813 [ dbSNP | Ensembl ].
VAR_020644
Natural varianti13 – 131T → R in Heather.
Corresponds to variant rs281864890 [ dbSNP | Ensembl ].
VAR_020645
Natural varianti16 – 161W → R in Catalonia. 1 Publication
Corresponds to variant rs34438981 [ dbSNP | Ensembl ].
VAR_003131
Natural varianti17 – 171G → R in Melbourne. 1 Publication
Corresponds to variant rs34907654 [ dbSNP | Ensembl ].
VAR_003132
Natural varianti18 – 181K → N in Clamart. 1 Publication
Corresponds to variant rs35621390 [ dbSNP | Ensembl ].
VAR_020646
Natural varianti20 – 201N → K in Ouled Rabah. 1 Publication
Corresponds to variant rs34018799 [ dbSNP | Ensembl ].
VAR_020647
Natural varianti21 – 211V → A in Bron. 1 Publication
Corresponds to variant rs63751196 [ dbSNP | Ensembl ].
VAR_030496
Natural varianti22 – 221E → K in Saskatoon. 1 Publication
Corresponds to variant rs33955330 [ dbSNP | Ensembl ].
VAR_003133
Natural varianti22 – 221E → Q in Fuchu. 1 Publication
Corresponds to variant rs33955330 [ dbSNP | Ensembl ].
VAR_003134
Natural varianti23 – 231D → G in Urumqi. 2 Publications
Corresponds to variant rs281864891 [ dbSNP | Ensembl ].
VAR_020648
Natural varianti23 – 231D → V in Granada. 1 Publication
Corresponds to variant rs281864891 [ dbSNP | Ensembl ].
VAR_003136
Natural varianti26 – 261G → E in Cosenza. 1 Publication
Corresponds to variant rs35687396 [ dbSNP | Ensembl ].
VAR_003137
Natural varianti27 – 271E → K in Oakland. 1 Publication
Corresponds to variant rs35654328 [ dbSNP | Ensembl ].
VAR_003139
Natural varianti35 – 351V → I in Tokyo. 1 Publication
Corresponds to variant rs35885783 [ dbSNP | Ensembl ].
VAR_003140
Natural varianti39 – 391T → P in Bonheiden; causes severe hereditary hemolytic anemia. 1 Publication
Corresponds to variant rs35799058 [ dbSNP | Ensembl ].
VAR_030497
Natural varianti41 – 411R → G in Veleta.
Corresponds to variant rs34532478 [ dbSNP | Ensembl ].
VAR_003144
Natural varianti41 – 411R → K in Austell. 1 Publication
Corresponds to variant rs281864892 [ dbSNP | Ensembl ].
VAR_020649
Natural varianti42 – 421F → S in TNCY; hemoglobin Cincinnati. 1 Publication
Corresponds to variant rs34878913 [ dbSNP | Ensembl ].
VAR_003146
Natural varianti45 – 451S → R in Lodz. 1 Publication
Corresponds to variant rs34017450 [ dbSNP | Ensembl ].
VAR_003148
Natural varianti56 – 561M → R in Kingston. 1 Publication
Corresponds to variant rs34915311 [ dbSNP | Ensembl ].
VAR_003150
Natural varianti60 – 601K → E in Emirates. 1 Publication
Corresponds to variant rs28933078 [ dbSNP | Ensembl ].
VAR_003151
Natural varianti60 – 601K → Q in Sacromonte. 1 Publication
Corresponds to variant rs28933078 [ dbSNP | Ensembl ].
VAR_003152
Natural varianti64 – 641H → L in TNCY; hemoglobin M-Circleville. 2 Publications
VAR_025336
Natural varianti64 – 641H → Y in TNCY; hemoglobin Osaka; the presence of a tyrosine causes the formation of a covalent link with heme iron, so that the iron is stabilized in the ferric form; when this occurs methemoglobin is formed, oxygen can no longer bind to heme and cyanosis occurs. 2 Publications
Corresponds to variant rs34474104 [ dbSNP | Ensembl ].
VAR_003154
Natural varianti66 – 661K → N in Clarke. 1 Publication
Corresponds to variant rs34019507 [ dbSNP | Ensembl ].
VAR_003155
Natural varianti67 – 671K → Q in Brooklyn. 1 Publication
Corresponds to variant rs34264694 [ dbSNP | Ensembl ].
VAR_003157
Natural varianti67 – 671K → R in Shanghai. 1 Publication
Corresponds to variant rs35481866 [ dbSNP | Ensembl ].
VAR_003156
Natural varianti68 – 681V → M in TNCY; hemoglobin Toms River; the side chain of methionine decreases both the affinity of oxygen for binding to the mutant hemoglobin subunit via steric hindrance and the rate at which it does so; the mutant methionine is converted to aspartic acid post-translationally. 1 Publication
Corresponds to variant rs587776864 [ dbSNP | Ensembl ].
VAR_065950
Natural varianti73 – 731G → R in Minoo. 1 Publication
Corresponds to variant rs281860594 [ dbSNP | Ensembl ].
VAR_020650
Natural varianti76 – 761I → T in LesVos/Waynesboro/Charlotte. 3 Publications
Corresponds to variant rs1061234 [ dbSNP | Ensembl ].
VAR_020651
Natural varianti76 – 761I → V in Coigneres. 1 Publication
Corresponds to variant rs34363111 [ dbSNP | Ensembl ].
VAR_030498
Natural varianti78 – 781H → R in Kennestone. 1 Publication
Corresponds to variant rs34150306 [ dbSNP | Ensembl ].
VAR_003162
Natural varianti81 – 811D → N in Marietta.
Corresponds to variant rs63751148 [ dbSNP | Ensembl ].
VAR_020652
Natural varianti93 – 931H → Y in TNCY; hemoglobin Fort Ripley. 1 Publication
Corresponds to variant rs35103459 [ dbSNP | Ensembl ].
VAR_003166
Natural varianti95 – 951D → N in Columbus-Ga. 1 Publication
Corresponds to variant rs35812514 [ dbSNP | Ensembl ].
VAR_003167
Natural varianti102 – 1021E → K in La Grange. 1 Publication
Corresponds to variant rs34876238 [ dbSNP | Ensembl ].
VAR_003169
Natural varianti105 – 1051K → N in Macedonia-II. 1 Publication
Corresponds to variant rs35717854 [ dbSNP | Ensembl ].
VAR_003170
Natural varianti106 – 1061L → H in TNCY; hemoglobin F-Brugine/Feldkirch; lowered affinity for oxygen. 1 Publication
VAR_073159
Natural varianti118 – 1181H → R in Malta-1. 1 Publication
Corresponds to variant rs36049074 [ dbSNP | Ensembl ].
VAR_003171
Natural varianti119 – 1191F → L in Calabria. 1 Publication
Corresponds to variant rs35020253 [ dbSNP | Ensembl ].
VAR_015740
Natural varianti121 – 1211K → Q in Caltech. 1 Publication
Corresponds to variant rs34703519 [ dbSNP | Ensembl ].
VAR_003172
Natural varianti122 – 1221E → K in Carlton. 1 Publication
Corresponds to variant rs63750021 [ dbSNP | Ensembl ].
VAR_020653
Natural varianti126 – 1261E → A in Port-Royal. 1 Publication
Corresponds to variant rs34997902 [ dbSNP | Ensembl ].
VAR_003174
Natural varianti131 – 1311W → G in Poole; unstable. 1 Publication
Corresponds to variant rs35826780 [ dbSNP | Ensembl ].
VAR_003176
Natural varianti147 – 1471H → Y in Onoda; O(2) affinity up. 1 Publication
Corresponds to variant rs34807671 [ dbSNP | Ensembl ].
VAR_003179

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
M91036 Genomic DNA. Translation: AAB59428.1.
M91037 Genomic DNA. Translation: AAA58492.1.
U01317 Genomic DNA. Translation: AAA16331.1.
V00515 Genomic DNA. Translation: CAA23773.1.
M15386 mRNA. Translation: AAB50159.1. Different initiation.
AY662983 Genomic DNA. Translation: AAT98611.1.
AK290492 mRNA. Translation: BAF83181.1.
BC010914 mRNA. Translation: AAH10914.1.
BC029387 mRNA. Translation: AAH29387.1.
BC130457 mRNA. Translation: AAI30458.1.
BC130459 mRNA. Translation: AAI30460.1.
M11427 mRNA. Translation: AAA35957.1.
CCDSiCCDS7755.1.
PIRiA90803. HGHUA.
RefSeqiNP_000175.1. NM_000184.2.
UniGeneiHs.302145.
Hs.702189.

Genome annotation databases

EnsembliENST00000336906; ENSP00000338082; ENSG00000196565.
ENST00000380259; ENSP00000369609; ENSG00000196565.
GeneIDi3048.
KEGGihsa:3048.
UCSCiuc001maj.2. human.

Keywords - Coding sequence diversityi

Polymorphism

Cross-referencesi

Web resourcesi

HbVar

Human hemoglobin variants and thalassemias

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
M91036 Genomic DNA. Translation: AAB59428.1.
M91037 Genomic DNA. Translation: AAA58492.1.
U01317 Genomic DNA. Translation: AAA16331.1.
V00515 Genomic DNA. Translation: CAA23773.1.
M15386 mRNA. Translation: AAB50159.1. Different initiation.
AY662983 Genomic DNA. Translation: AAT98611.1.
AK290492 mRNA. Translation: BAF83181.1.
BC010914 mRNA. Translation: AAH10914.1.
BC029387 mRNA. Translation: AAH29387.1.
BC130457 mRNA. Translation: AAI30458.1.
BC130459 mRNA. Translation: AAI30460.1.
M11427 mRNA. Translation: AAA35957.1.
CCDSiCCDS7755.1.
PIRiA90803. HGHUA.
RefSeqiNP_000175.1. NM_000184.2.
UniGeneiHs.302145.
Hs.702189.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
1FDHX-ray2.50G/H2-147[»]
4MQJX-ray1.80B/D/F/H3-147[»]
4MQKX-ray2.24B/D/F/H2-147[»]
ProteinModelPortaliP69892.
SMRiP69892. Positions 3-147.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi109298. 8 interactions.
IntActiP69892. 6 interactions.
MINTiMINT-1200269.
STRINGi9606.ENSP00000338082.

PTM databases

iPTMnetiP69892.
PhosphoSiteiP69892.

Polymorphism and mutation databases

BioMutaiHBG2.
DMDMi56749861.

Proteomic databases

EPDiP69892.
MaxQBiP69892.
PaxDbiP69892.
PeptideAtlasiP69892.
PRIDEiP69892.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsembliENST00000336906; ENSP00000338082; ENSG00000196565.
ENST00000380259; ENSP00000369609; ENSG00000196565.
GeneIDi3048.
KEGGihsa:3048.
UCSCiuc001maj.2. human.

Organism-specific databases

CTDi3048.
GeneCardsiHBG2.
HGNCiHGNC:4832. HBG2.
HPAiCAB016143.
HPA043234.
MalaCardsiHBG2.
MIMi142250. gene.
613977. phenotype.
neXtProtiNX_P69892.
Orphaneti280615. Hemoglobinopathy Toms River.
46532. Hereditary persistence of fetal hemoglobin - beta-thalassemia.
251380. Hereditary persistence of fetal hemoglobin - sickle cell disease.
PharmGKBiPA29207.
GenAtlasiSearch...

Phylogenomic databases

eggNOGiKOG3378. Eukaryota.
COG1018. LUCA.
GeneTreeiENSGT00760000119197.
HOVERGENiHBG009709.
InParanoidiP69892.
KOiK13824.
PhylomeDBiP69892.
TreeFamiTF333268.

Enzyme and pathway databases

ReactomeiR-HSA-983231. Factors involved in megakaryocyte development and platelet production.

Miscellaneous databases

ChiTaRSiHBG2. human.
EvolutionaryTraceiP69892.
GeneWikiiHBG2.
GenomeRNAii3048.
PROiP69892.
SOURCEiSearch...

Gene expression databases

BgeeiENSG00000196565.
CleanExiHS_HBG2.
ExpressionAtlasiP69892. baseline and differential.
GenevisibleiP69892. HS.

Family and domain databases

CDDicd08925. Hb-beta_like. 1 hit.
Gene3Di1.10.490.10. 1 hit.
InterProiIPR000971. Globin.
IPR009050. Globin-like.
IPR012292. Globin/Proto.
IPR002337. Haemoglobin_b.
[Graphical view]
PfamiPF00042. Globin. 1 hit.
[Graphical view]
PRINTSiPR00814. BETAHAEM.
SUPFAMiSSF46458. SSF46458. 1 hit.
PROSITEiPS01033. GLOBIN. 1 hit.
[Graphical view]
ProtoNetiSearch...

Entry informationi

Entry nameiHBG2_HUMAN
AccessioniPrimary (citable) accession number: P69892
Secondary accession number(s): A8MZE0
, P02096, P62027, Q14491, Q68NH9, Q96FH6, Q96FH7
Entry historyi
Integrated into UniProtKB/Swiss-Prot: July 21, 1986
Last sequence update: January 23, 2007
Last modified: September 7, 2016
This is version 131 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, Direct protein sequencing, 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. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  6. 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.