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Protein

Protein son of sevenless

Gene

Sos

Organism
Drosophila melanogaster (Fruit fly)
Status
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli

Functioni

Promotes the exchange of Ras-bound GDP by GTP. Functions in signaling pathways initiated by the sevenless and epidermal growth factor receptor tyrosine kinases; implies a role for the ras pathway in neuronal development.2 Publications

GO - Molecular functioni

  • DNA binding Source: InterPro
  • Rac guanyl-nucleotide exchange factor activity Source: FlyBase
  • Ras guanyl-nucleotide exchange factor activity Source: FlyBase

GO - Biological processi

  • actin filament organization Source: FlyBase
  • anterior/posterior axis specification, embryo Source: FlyBase
  • axon midline choice point recognition Source: FlyBase
  • imaginal disc-derived leg morphogenesis Source: FlyBase
  • negative regulation of G1/S transition of mitotic cell cycle Source: FlyBase
  • positive regulation of Rac protein signal transduction Source: FlyBase
  • positive regulation of Ras protein signal transduction Source: FlyBase
  • regulation of cell shape Source: FlyBase
  • regulation of Rho protein signal transduction Source: InterPro
  • sevenless signaling pathway Source: FlyBase
  • small GTPase mediated signal transduction Source: InterPro
  • torso signaling pathway Source: FlyBase
  • tracheal outgrowth, open tracheal system Source: FlyBase
Complete GO annotation...

Keywords - Molecular functioni

Developmental protein, Guanine-nucleotide releasing factor

Keywords - Biological processi

Differentiation, Neurogenesis

Enzyme and pathway databases

ReactomeiR-DME-112412. SOS-mediated signalling.
R-DME-1250347. SHC1 events in ERBB4 signaling.
R-DME-1433557. Signaling by SCF-KIT.
R-DME-1433559. Regulation of KIT signaling.
R-DME-167044. Signalling to RAS.
R-DME-179812. GRB2 events in EGFR signaling.
R-DME-180336. SHC1 events in EGFR signaling.
R-DME-193648. NRAGE signals death through JNK.
R-DME-194840. Rho GTPase cycle.
R-DME-1963640. GRB2 events in ERBB2 signaling.
R-DME-210993. Tie2 Signaling.
R-DME-2179392. EGFR Transactivation by Gastrin.
R-DME-2424491. DAP12 signaling.
R-DME-2428933. SHC-related events triggered by IGF1R.
R-DME-2730905. Role of LAT2/NTAL/LAB on calcium mobilization.
R-DME-2871796. FCERI mediated MAPK activation.
R-DME-354194. GRB2:SOS provides linkage to MAPK signaling for Integrins.
R-DME-375165. NCAM signaling for neurite out-growth.
R-DME-416482. G alpha (12/13) signalling events.
R-DME-428540. Activation of Rac.
R-DME-5654688. SHC-mediated cascade:FGFR1.
R-DME-5654693. FRS-mediated FGFR1 signaling.
R-DME-5654699. SHC-mediated cascade:FGFR2.
R-DME-5654700. FRS-mediated FGFR2 signaling.
R-DME-5654704. SHC-mediated cascade:FGFR3.
R-DME-5654706. FRS-mediated FGFR3 signaling.
R-DME-5654712. FRS-mediated FGFR4 signaling.
R-DME-5654719. SHC-mediated cascade:FGFR4.
R-DME-5673001. RAF/MAP kinase cascade.
R-DME-74749. Signal attenuation.
R-DME-74751. Insulin receptor signalling cascade.
R-DME-8851805. MET activates RAS signaling.
SignaLinkiP26675.

Names & Taxonomyi

Protein namesi
Recommended name:
Protein son of sevenless
Gene namesi
Name:Sos
ORF Names:CG7793
OrganismiDrosophila melanogaster (Fruit fly)
Taxonomic identifieri7227 [NCBI]
Taxonomic lineageiEukaryotaMetazoaEcdysozoaArthropodaHexapodaInsectaPterygotaNeopteraEndopterygotaDipteraBrachyceraMuscomorphaEphydroideaDrosophilidaeDrosophilaSophophora
Proteomesi
  • UP000000803 Componenti: Chromosome 2L

Organism-specific databases

FlyBaseiFBgn0001965. Sos.

Subcellular locationi

GO - Cellular componenti

  • cytoplasm Source: FlyBase
  • cytosol Source: Reactome
  • extrinsic component of cytoplasmic side of plasma membrane Source: FlyBase
Complete GO annotation...

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
ChainiPRO_00000688981 – 1596Protein son of sevenlessAdd BLAST1596

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Modified residuei1550Phosphoserine1 Publication1
Modified residuei1551Phosphoserine1 Publication1

Keywords - PTMi

Phosphoprotein

Proteomic databases

PaxDbiP26675.
PRIDEiP26675.

PTM databases

iPTMnetiP26675.

Expressioni

Gene expression databases

BgeeiFBgn0001965.
GenevisibleiP26675. DM.

Interactioni

Subunit structurei

May form a complex with sevenless and DRK.

Protein-protein interaction databases

BioGridi60823. 10 interactors.
DIPiDIP-22308N.
IntActiP26675. 12 interactors.
MINTiMINT-315092.
STRINGi7227.FBpp0080118.

Structurei

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
1AZENMR-B1342-1350[»]
ProteinModelPortaliP26675.
SMRiP26675.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiP26675.

Family & Domainsi

Domains and Repeats

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Domaini248 – 434DHPROSITE-ProRule annotationAdd BLAST187
Domaini480 – 588PHPROSITE-ProRule annotationAdd BLAST109
Domaini637 – 792N-terminal Ras-GEFPROSITE-ProRule annotationAdd BLAST156
Domaini829 – 1066Ras-GEFPROSITE-ProRule annotationAdd BLAST238

Compositional bias

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Compositional biasi4 – 51Gly-richAdd BLAST48
Compositional biasi1110 – 1146Ala-richAdd BLAST37
Compositional biasi1519 – 1542His-richAdd BLAST24

Sequence similaritiesi

Contains 1 DH (DBL-homology) domain.PROSITE-ProRule annotation
Contains 1 N-terminal Ras-GEF domain.PROSITE-ProRule annotation
Contains 1 PH domain.PROSITE-ProRule annotation
Contains 1 Ras-GEF domain.PROSITE-ProRule annotation

Phylogenomic databases

eggNOGiKOG3417. Eukaryota.
ENOG410XR96. LUCA.
GeneTreeiENSGT00860000133664.
InParanoidiP26675.
KOiK03099.
OMAiMATNMEY.
OrthoDBiEOG091G04UL.
PhylomeDBiP26675.

Family and domain databases

CDDicd00155. RasGEF. 1 hit.
cd06224. REM. 1 hit.
Gene3Di1.10.20.10. 1 hit.
1.10.840.10. 1 hit.
1.20.900.10. 1 hit.
2.30.29.30. 1 hit.
InterProiIPR000219. DH-domain.
IPR009072. Histone-fold.
IPR007125. Histone_H2A/H2B/H3.
IPR011993. PH_dom-like.
IPR001849. PH_domain.
IPR000651. Ras-like_Gua-exchang_fac_N.
IPR019804. Ras_G-nucl-exch_fac_CS.
IPR023578. Ras_GEF_dom.
IPR001895. RASGEF_cat_dom.
[Graphical view]
PfamiPF00125. Histone. 1 hit.
PF00169. PH. 1 hit.
PF00617. RasGEF. 1 hit.
PF00618. RasGEF_N. 1 hit.
PF00621. RhoGEF. 1 hit.
[Graphical view]
SMARTiSM00233. PH. 1 hit.
SM00147. RasGEF. 1 hit.
SM00229. RasGEFN. 1 hit.
SM00325. RhoGEF. 1 hit.
[Graphical view]
SUPFAMiSSF47113. SSF47113. 1 hit.
SSF48065. SSF48065. 1 hit.
SSF48366. SSF48366. 1 hit.
SSF50729. SSF50729. 1 hit.
PROSITEiPS50010. DH_2. 1 hit.
PS50003. PH_DOMAIN. 1 hit.
PS00720. RASGEF. 1 hit.
PS50009. RASGEF_CAT. 1 hit.
PS50212. RASGEF_NTER. 1 hit.
[Graphical view]

Sequencei

Sequence statusi: Complete.

P26675-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MFSGPSGHAH TISYGGGIGL GTGGGGGSGG SGSGSQGGGG GIGIGGGGVA
60 70 80 90 100
GLQDCDGYDF TKCENAARWR GLFTPSLKKV LEQVHPRVTA KEDALLYVEK
110 120 130 140 150
LCLRLLAMLC AKPLPHSVQD VEEKVNKSFP APIDQWALNE AKEVINSKKR
160 170 180 190 200
KSVLPTEKVH TLLQKDVLQY KIDSSVSAFL VAVLEYISAD ILKMAGDYVI
210 220 230 240 250
KIAHCEITKE DIEVVMNADR VLMDMLNQSE AHILPSPLSL PAQRASATYE
260 270 280 290 300
ETVKELIHDE KQYQRDLHMI IRVFREELVK IVSDPRELEP IFSNIMDIYE
310 320 330 340 350
VTVTLLGSLE DVIEMSQEQS APCVGSCFEE LAEAEEFDVY KKYAYDVTSQ
360 370 380 390 400
ASRDALNNLL SKPGASSLTT AGHGFRDAVK YYLPKLLLVP ICHAFVYFDY
410 420 430 440 450
IKHLKDLSSS QDDIESFEQV QGLLHPLHCD LEKVMASLSK ERQVPVSGRV
460 470 480 490 500
RRQLAIERTR ELQMKVEHWE DKDVGQNCNE FIREDSLSKL GSGKRIWSER
510 520 530 540 550
KVFLFDGLMV LCKANTKKQT PSAGATAYDY RLKEKYFMRR VDINDRPDSD
560 570 580 590 600
DLKNSFELAP RMQPPIVLTA KNAQHKHDWM ADLLMVITKS MLDRHLDSIL
610 620 630 640 650
QDIERKHPLR MPSPEIYKFA VPDSGDNIVL EERESAGVPM IKGATLCKLI
660 670 680 690 700
ERLTYHIYAD PTFVRTFLTT YRYFCSPQQL LQLLVERFNI PDPSLVYQDT
710 720 730 740 750
GTAGAGGMGG VGGDKEHKNS HREDWKRYRK EYVQPVQFRV LNVLRHWVDH
760 770 780 790 800
HFYDFEKDPM LLEKLLNFLE HVNGKSMRKW VDSVLKIVQR KNEQEKSNKK
810 820 830 840 850
IVYAYGHDPP PIEHHLSVPN DEITLLTLHP LELARQLTLL EFEMYKNVKP
860 870 880 890 900
SELVGSPWTK KDKEVKSPNL LKIMKHTTNV TRWIEKSITE AENYEERLAI
910 920 930 940 950
MQRAIEVMMV MLELNNFNGI LSIVAAMGTA SVYRLRWTFQ GLPERYRKFL
960 970 980 990 1000
EECRELSDDH LKKYQERLRS INPPCVPFFG RYLTNILHLE EGNPDLLANT
1010 1020 1030 1040 1050
ELINFSKRRK VAEIIGEIQQ YQNQPYCLNE ESTIRQFFEQ LDPFNGLSDK
1060 1070 1080 1090 1100
QMSDYLYNES LRIEPRGCKT VPKFPRKWPH IPLKSPGIKP RRQNQTNSSS
1110 1120 1130 1140 1150
KLSNSTSSVA AAAAASSTAT SIATASAPSL HASSIMDAPT AAAANAGSGT
1160 1170 1180 1190 1200
LAGEQSPQHN PHAFSVFAPV IIPERNTSSW SGTPQHTRTD QNNGEVSVPA
1210 1220 1230 1240 1250
PHLPKKPGAH VWANNNSTLA SASAMDVVFS PALPEHLPPQ SLPDSNPFAS
1260 1270 1280 1290 1300
DTEAPPSPLP KLVVSPRHET GNRSPFHGRM QNSPTHSTAS TVTLTGMSTS
1310 1320 1330 1340 1350
GGEEFCAGGF YFNSAHQGQP GAVPISPHVN VPMATNMEYR AVPPPLPPRR
1360 1370 1380 1390 1400
KERTESCADM AQKRQAPDAP TLPPRDGELS PPPIPPRLNH STGISYLRQS
1410 1420 1430 1440 1450
HGKSKEFVGN SSLLLPNTSS IMIRRNSAIE KRAAATSQPN QAAAGPISTT
1460 1470 1480 1490 1500
LVTVSQAVAT DEPLPLPISP AASSSTTTSP LTPAMSPMSP NIPSHPVEST
1510 1520 1530 1540 1550
SSSYAHQLRM RQQQQQQTHP AIYSQHHQHH ATHLPHHPHQ HHSNPTQSRS
1560 1570 1580 1590
SPKEFFPIAT SLEGTPKLPP KPSLSANFYN NPDKGTMFLY PSTNEE
Length:1,596
Mass (Da):177,934
Last modified:September 27, 2005 - v2
Checksum:i08DB85B59213B964
GO

Sequence cautioni

The sequence AAL13978 differs from that shown. Reason: Erroneous initiation.Curated

Experimental Info

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sequence conflicti15G → W in AAT94523 (Ref. 6) Curated1
Sequence conflicti232 – 244HILPS…LPAQR → TSCPVPCHFPRS (PubMed:1736363).CuratedAdd BLAST13
Sequence conflicti523A → T in AAT94523 (Ref. 6) Curated1
Sequence conflicti1463P → V in AAB04680 (PubMed:1736363).Curated1
Sequence conflicti1468I → V in AAT94523 (Ref. 6) Curated1

Natural variant

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Natural varianti1256P → L in strain: St_L028 and St_L033. 1
Natural varianti1322A → S in strain: In_L019. 1
Natural varianti1503S → N in strain: In_L019. 1

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
M83931 mRNA. Translation: AAB04680.1.
M77501 Genomic DNA. Translation: AAA28904.1.
AE014134 Genomic DNA. Translation: AAF53336.2.
BT015294 mRNA. Translation: AAT94523.1.
AY058749 mRNA. Translation: AAL13978.1. Different initiation.
AF459566 Genomic DNA. Translation: AAN61382.1.
AF459567 Genomic DNA. Translation: AAN61383.1.
AF459568 Genomic DNA. Translation: AAN61384.1.
AF459569 Genomic DNA. Translation: AAN61385.1.
AF459570 Genomic DNA. Translation: AAN61386.1.
AF459571 Genomic DNA. Translation: AAN61387.1.
AF459572 Genomic DNA. Translation: AAN61388.1.
AF459573 Genomic DNA. Translation: AAN61389.1.
AF459574 Genomic DNA. Translation: AAN61390.1.
AF459575 Genomic DNA. Translation: AAN61391.1.
AF459576 Genomic DNA. Translation: AAN61392.1.
AF459577 Genomic DNA. Translation: AAN61393.1.
AF459578 Genomic DNA. Translation: AAN61394.1.
AF459579 Genomic DNA. Translation: AAN61395.1.
AF459580 Genomic DNA. Translation: AAN61396.1.
AF459581 Genomic DNA. Translation: AAN61397.1.
AF459582 Genomic DNA. Translation: AAN61398.1.
AF459583 Genomic DNA. Translation: AAN61399.1.
AF459584 Genomic DNA. Translation: AAN61400.1.
AF459585 Genomic DNA. Translation: AAN61401.1.
PIRiA41216.
RefSeqiNP_476597.2. NM_057249.6.

Genome annotation databases

EnsemblMetazoaiFBtr0080541; FBpp0080118; FBgn0001965.
GeneIDi34790.
KEGGidme:Dmel_CG7793.

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
M83931 mRNA. Translation: AAB04680.1.
M77501 Genomic DNA. Translation: AAA28904.1.
AE014134 Genomic DNA. Translation: AAF53336.2.
BT015294 mRNA. Translation: AAT94523.1.
AY058749 mRNA. Translation: AAL13978.1. Different initiation.
AF459566 Genomic DNA. Translation: AAN61382.1.
AF459567 Genomic DNA. Translation: AAN61383.1.
AF459568 Genomic DNA. Translation: AAN61384.1.
AF459569 Genomic DNA. Translation: AAN61385.1.
AF459570 Genomic DNA. Translation: AAN61386.1.
AF459571 Genomic DNA. Translation: AAN61387.1.
AF459572 Genomic DNA. Translation: AAN61388.1.
AF459573 Genomic DNA. Translation: AAN61389.1.
AF459574 Genomic DNA. Translation: AAN61390.1.
AF459575 Genomic DNA. Translation: AAN61391.1.
AF459576 Genomic DNA. Translation: AAN61392.1.
AF459577 Genomic DNA. Translation: AAN61393.1.
AF459578 Genomic DNA. Translation: AAN61394.1.
AF459579 Genomic DNA. Translation: AAN61395.1.
AF459580 Genomic DNA. Translation: AAN61396.1.
AF459581 Genomic DNA. Translation: AAN61397.1.
AF459582 Genomic DNA. Translation: AAN61398.1.
AF459583 Genomic DNA. Translation: AAN61399.1.
AF459584 Genomic DNA. Translation: AAN61400.1.
AF459585 Genomic DNA. Translation: AAN61401.1.
PIRiA41216.
RefSeqiNP_476597.2. NM_057249.6.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum
1AZENMR-B1342-1350[»]
ProteinModelPortaliP26675.
SMRiP26675.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi60823. 10 interactors.
DIPiDIP-22308N.
IntActiP26675. 12 interactors.
MINTiMINT-315092.
STRINGi7227.FBpp0080118.

PTM databases

iPTMnetiP26675.

Proteomic databases

PaxDbiP26675.
PRIDEiP26675.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsemblMetazoaiFBtr0080541; FBpp0080118; FBgn0001965.
GeneIDi34790.
KEGGidme:Dmel_CG7793.

Organism-specific databases

CTDi34790.
FlyBaseiFBgn0001965. Sos.

Phylogenomic databases

eggNOGiKOG3417. Eukaryota.
ENOG410XR96. LUCA.
GeneTreeiENSGT00860000133664.
InParanoidiP26675.
KOiK03099.
OMAiMATNMEY.
OrthoDBiEOG091G04UL.
PhylomeDBiP26675.

Enzyme and pathway databases

ReactomeiR-DME-112412. SOS-mediated signalling.
R-DME-1250347. SHC1 events in ERBB4 signaling.
R-DME-1433557. Signaling by SCF-KIT.
R-DME-1433559. Regulation of KIT signaling.
R-DME-167044. Signalling to RAS.
R-DME-179812. GRB2 events in EGFR signaling.
R-DME-180336. SHC1 events in EGFR signaling.
R-DME-193648. NRAGE signals death through JNK.
R-DME-194840. Rho GTPase cycle.
R-DME-1963640. GRB2 events in ERBB2 signaling.
R-DME-210993. Tie2 Signaling.
R-DME-2179392. EGFR Transactivation by Gastrin.
R-DME-2424491. DAP12 signaling.
R-DME-2428933. SHC-related events triggered by IGF1R.
R-DME-2730905. Role of LAT2/NTAL/LAB on calcium mobilization.
R-DME-2871796. FCERI mediated MAPK activation.
R-DME-354194. GRB2:SOS provides linkage to MAPK signaling for Integrins.
R-DME-375165. NCAM signaling for neurite out-growth.
R-DME-416482. G alpha (12/13) signalling events.
R-DME-428540. Activation of Rac.
R-DME-5654688. SHC-mediated cascade:FGFR1.
R-DME-5654693. FRS-mediated FGFR1 signaling.
R-DME-5654699. SHC-mediated cascade:FGFR2.
R-DME-5654700. FRS-mediated FGFR2 signaling.
R-DME-5654704. SHC-mediated cascade:FGFR3.
R-DME-5654706. FRS-mediated FGFR3 signaling.
R-DME-5654712. FRS-mediated FGFR4 signaling.
R-DME-5654719. SHC-mediated cascade:FGFR4.
R-DME-5673001. RAF/MAP kinase cascade.
R-DME-74749. Signal attenuation.
R-DME-74751. Insulin receptor signalling cascade.
R-DME-8851805. MET activates RAS signaling.
SignaLinkiP26675.

Miscellaneous databases

EvolutionaryTraceiP26675.
GenomeRNAii34790.
PROiP26675.

Gene expression databases

BgeeiFBgn0001965.
GenevisibleiP26675. DM.

Family and domain databases

CDDicd00155. RasGEF. 1 hit.
cd06224. REM. 1 hit.
Gene3Di1.10.20.10. 1 hit.
1.10.840.10. 1 hit.
1.20.900.10. 1 hit.
2.30.29.30. 1 hit.
InterProiIPR000219. DH-domain.
IPR009072. Histone-fold.
IPR007125. Histone_H2A/H2B/H3.
IPR011993. PH_dom-like.
IPR001849. PH_domain.
IPR000651. Ras-like_Gua-exchang_fac_N.
IPR019804. Ras_G-nucl-exch_fac_CS.
IPR023578. Ras_GEF_dom.
IPR001895. RASGEF_cat_dom.
[Graphical view]
PfamiPF00125. Histone. 1 hit.
PF00169. PH. 1 hit.
PF00617. RasGEF. 1 hit.
PF00618. RasGEF_N. 1 hit.
PF00621. RhoGEF. 1 hit.
[Graphical view]
SMARTiSM00233. PH. 1 hit.
SM00147. RasGEF. 1 hit.
SM00229. RasGEFN. 1 hit.
SM00325. RhoGEF. 1 hit.
[Graphical view]
SUPFAMiSSF47113. SSF47113. 1 hit.
SSF48065. SSF48065. 1 hit.
SSF48366. SSF48366. 1 hit.
SSF50729. SSF50729. 1 hit.
PROSITEiPS50010. DH_2. 1 hit.
PS50003. PH_DOMAIN. 1 hit.
PS00720. RASGEF. 1 hit.
PS50009. RASGEF_CAT. 1 hit.
PS50212. RASGEF_NTER. 1 hit.
[Graphical view]
ProtoNetiSearch...

Entry informationi

Entry nameiSOS_DROME
AccessioniPrimary (citable) accession number: P26675
Secondary accession number(s): Q6AWF4
, Q8I067, Q8I0F7, Q8ITK2, Q95TI8, Q969D6, Q9VJV9
Entry historyi
Integrated into UniProtKB/Swiss-Prot: August 1, 1992
Last sequence update: September 27, 2005
Last modified: November 30, 2016
This is version 169 of the entry and version 2 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programDrosophila annotation project

Miscellaneousi

Keywords - Technical termi

3D-structure, Complete proteome, Reference proteome

Documents

  1. Drosophila
    Drosophila: entries, gene names and cross-references to FlyBase
  2. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  3. 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.