Seroatlas · Human Serome Atlas

MAP3K21

Mitogen-activated protein kinase kinase kinase 21

Also known as: KIAA1804, M3K21_HUMAN, MLK4

Cross-references: UniProt · Ensembl · Human Protein Atlas · GeneCards · NCBI Gene

Protein identityUniProt · HPA

UniProt accession: Q5TCX8
Gene: MAP3K21
Ensembl: ENSG00000143674
Chromosome: 1
Canonical length: 1036 aa
Protein class: Enzymes, Predicted intracellular proteins
Subcellular location: Plasma membrane,Cytosol
Quaternary structure: Homodimer

OverviewNCBI Gene

Predicted to enable JUN kinase kinase kinase activity and protein homodimerization activity. Predicted to be involved in protein autophosphorylation and signal transduction. Predicted to be active in cytoplasm. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

1036 residues, UniProt reviewed canonical sequence.

>Q5TCX8|MAP3K21
     1  MALRGAAGAT DTPVSSAGGA PGGSASSSST SSGGSASAGA GLWAALYDYE ARGEDELSLR
    61  RGQLVEVLSQ DAAVSGDEGW WAGQVQRRLG IFPANYVAPC RPAASPAPPP SRPSSPVHVA
   121  FERLELKELI GAGGFGQVYR ATWQGQEVAV KAARQDPEQD AAAAAESVRR EARLFAMLRH
   181  PNIIELRGVC LQQPHLCLVL EFARGGALNR ALAAANAAPD PRAPGPRRAR RIPPHVLVNW
   241  AVQIARGMLY LHEEAFVPIL HRDLKSSNIL LLEKIEHDDI CNKTLKITDF GLAREWHRTT
   301  KMSTAGTYAW MAPEVIKSSL FSKGSDIWSY GVLLWELLTG EVPYRGIDGL AVAYGVAVNK
   361  LTLPIPSTCP EPFAKLMKEC WQQDPHIRPS FALILEQLTA IEGAVMTEMP QESFHSMQDD
   421  WKLEIQQMFD ELRTKEKELR SREEELTRAA LQQKSQEELL KRREQQLAER EIDVLERELN
   481  ILIFQLNQEK PKVKKRKGKF KRSRLKLKDG HRISLPSDFQ HKITVQASPN LDKRRSLNSS
   541  SSSPPSSPTM MPRLRAIQLT SDESNKTWGR NTVFRQEEFE DVKRNFKKKG CTWGPNSIQM
   601  KDRTDCKERI RPLSDGNSPW STILIKNQKT MPLASLFVDQ PGSCEEPKLS PDGLEHRKPK
   661  QIKLPSQAYI DLPLGKDAQR ENPAEAESWE EAASANAATV SIEMTPTNSL SRSPQRKKTE
   721  SALYGCTVLL ASVALGLDLR ELHKAQAAEE PLPKEEKKKR EGIFQRASKS RRSASPPTSL
   781  PSTCGEASSP PSLPLSSALG ILSTPSFSTK CLLQMDSEDP LVDSAPVTCD SEMLTPDFCP
   841  TAPGSGREPA LMPRLDTDCS VSRNLPSSFL QQTCGNVPYC ASSKHRPSHH RRTMSDGNPT
   901  PTGATIISAT GASALPLCPS PAPHSHLPRE VSPKKHSTVH IVPQRRPASL RSRSDLPQAY
   961  PQTAVSQLAQ TACVVGRPGP HPTQFLAAKE RTKSHVPSLL DADVEGQSRD YTVPLCRMRS
  1021  KTSRPSIYEL EKEFLS

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against MAP3K21 can act on the native protein depends on physical access: surface and secreted proteins are reachable by circulating antibodies, intracellular proteins usually are not.

Antibody reachability: Intracellular
Secreted: No
Transmembrane segments: 0
Mean surface accessibility (rSASA): 0.54
Highest tissue expression: 19 nTPM

Expression across tissuesHPA

Tissue

pancreas: 19 nTPM
stomach: 12 nTPM
duodenum: 11 nTPM
kidney: 11 nTPM
small intestine: 9.5 nTPM
testis: 8.8 nTPM

Single-cell type

renal connecting tubule cells: 245 nCPM
sertoli cells: 243 nCPM
renal collecting duct principal cells: 166 nCPM
parietal cells: 145 nCPM
pancreatic duct cells: 142 nCPM
pancreatic acinar cells: 109 nCPM

Immune cell

NK-cell: 1.6 nTPM
myeloid DC: 0.3 nTPM
classical monocyte: 0.1 nTPM
memory B-cell: 0.1 nTPM
naive B-cell: 0.1 nTPM
plasmacytoid DC: 0.1 nTPM

Brain region

cerebellum: 15 nTPM
cerebral cortex: 8.6 nTPM
hypothalamus: 7.4 nTPM
basal ganglia: 7.3 nTPM
pons: 7.2 nTPM
white matter: 6.2 nTPM

Genetic constraint and essentialitygnomAD · DepMap

Does the body need this protein intact? Low LOEUF or a strong DepMap dependency means loss or blockade of the protein is likely to be felt.

gnomAD LOEUF (loss-of-function intolerance): 0.69
gnomAD pLI: 0
DepMap mean gene effect: -0.06
DepMap dependency class: selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 8% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Molecular functions

Cellular components

cytoplasm

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of MAP3K21 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads MAP3K21 as an antibody target. Whether an autoantibody or antibody against MAP3K21 could matter depends on whether native MAP3K21 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

MAP3K21 is annotated as predominantly intracellular. Intracellular proteins are common autoantibody markers, becoming visible to the immune system after cell injury or altered processing, but are usually markers of disease rather than direct drivers.

Annotation status

The present source text does not explicitly label MAP3K21 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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