Seroatlas · Human Serome Atlas

MB21D2

Nucleotidyltransferase MB21D2

Also known as: C3orf59, M21D2_HUMAN

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

Protein identityUniProt · HPA

UniProt accession: Q8IYB1
Gene: MB21D2
Ensembl: ENSG00000180611
Chromosome: 3
Canonical length: 491 aa
Protein class: Predicted intracellular proteins
Subcellular location: Cytosol

OverviewNCBI Gene

Enables cadherin binding activity. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

491 residues, UniProt reviewed canonical sequence.

>Q8IYB1|MB21D2
     1  MKMAAPTANK AASLGCNNKP AFPELDFRSG ARVEELNKLI QEFTKHDQRE YDDQRALEIH
    61  TAKDFIFSML GMVQKLDQKL PVANEYLLLS GGVREGVVDL DLDELNVYAR GTDYDMDFTL
   121  LVPALKLHDR NQPVTLDMRH SALCHSWLSL RLFDEGTISK WKDCCTIVDH INGATNYFFS
   181  PTKVADWFYD SISIVLSEIQ KKPQRGMPKV EKVEKNGTII SIILGVGSSR MLYDIVPVVS
   241  FKGWPAVAQS WLMENHFWDG KITEEEVISG FYLVPACSYK GKKDNEWRLS FARSEVQLKK
   301  CISSSLMQAY QACKAIIIKL LSRPKAISPY HLRSMMLWAC DRLPANYLAQ EDYAAHFLLG
   361  LIDDLQHCLV NKMCPNYFIP QCNMLEHLSE ETVMLHARKL SSVRSDPAEH LRTAIEHVKA
   421  ANRLTLELQR RGSTTSIPSP QSDGGDPNQP DDRLAKKLQQ LVTENPGKSI SVFINPDDVT
   481  RPHFRIDDKF F

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against MB21D2 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: Unknown
Secreted: No
Transmembrane segments: 0
Mean surface accessibility (rSASA): 0.28
Highest tissue expression: 13 nTPM

Expression across tissuesHPA

Tissue

placenta: 13 nTPM
small intestine: 8.7 nTPM
duodenum: 8.3 nTPM
urinary bladder: 8.3 nTPM
testis: 6.7 nTPM
cerebellum: 5.4 nTPM

Single-cell type

syncytiotrophoblasts: 424 nCPM
endometrial luminal cells: 332 nCPM
cytotrophoblasts: 319 nCPM
urothelial cells: 235 nCPM
thyrotrophs: 218 nCPM
cdc: 212 nCPM

Immune cell

memory CD4 T-cell: 4.2 nTPM
T-reg: 3.9 nTPM
naive CD4 T-cell: 2.6 nTPM
MAIT T-cell: 1.9 nTPM
memory CD8 T-cell: 1 nTPM
total PBMC: 0.9 nTPM

Brain region

cerebellum: 7.7 nTPM
cerebral cortex: 6.7 nTPM
basal ganglia: 6.6 nTPM
hypothalamus: 5.7 nTPM
white matter: 5.7 nTPM
medulla oblongata: 5.3 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: 0.04
gnomAD missense Z: 1.19
DepMap mean gene effect: -0.06
DepMap dependency class: none

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

Molecular functions

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of MB21D2 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 MB21D2 as an antibody target. Whether an autoantibody or antibody against MB21D2 could matter depends on whether native MB21D2 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

MB21D2 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 MB21D2 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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