Seroatlas · Human Serome Atlas

TBC1D21

TBC1 domain family member 21

Also known as: MGC34741, MgcRabGAP, TBC21_HUMAN

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

Protein identityUniProt · HPA

UniProt accession: Q8IYX1
Gene: TBC1D21
Ensembl: ENSG00000167139
Chromosome: 15
Canonical length: 336 aa
Protein class: Predicted intracellular proteins
Subcellular location: Calyx,Mid piece

OverviewNCBI Gene

Enables GTPase activator activity and small GTPase binding activity. Predicted to be involved in plasma membrane to endosome transport; sperm axoneme assembly; and sperm mitochondrial sheath assembly. Located in extracellular exosome. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

336 residues, UniProt reviewed canonical sequence.

>Q8IYX1|TBC1D21
     1  MTTLSPENSL SARQSASFIL VKRKPPIDKT EWDSFFDESG HLAKSRDFIC VNILERGLHP
    61  FVRTEAWKFL TGYFSWQSSQ DERLTVDSMR RKNYKALCQM YEKIQPLLEN LHRNFTETRN
   121  NIARDIQKIY DKDPLGNVLI DKKRLEKILL LSYVCNTQAE YQQGFHEMMM LFQLMVEHDH
   181  ETFWLFQFFL QKTEHSCVIN IGVAKNLDML STLITFLDPV FAEHLKGKGA GAVQSLFPWF
   241  CFCFQRAFKS FDDVWRLWEV LLTGKPCRNF QVLVAYSMLQ MVREQVLQES MGGDDILLAC
   301  NNLIDLDADE LISAACVVYA ELIQKDVPQT LKDFFL

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against TBC1D21 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): 0.25
Highest tissue expression: 46 nTPM

Expression across tissuesHPA

Tissue

testis: 46 nTPM
adipose tissue: 0 nTPM
adrenal gland: 0 nTPM
amygdala: 0 nTPM
appendix: 0 nTPM
basal ganglia: 0 nTPM

Single-cell type

late spermatids: 1,707 nCPM
early spermatids: 475 nCPM
late primary spermatocytes: 189 nCPM
peritubular myoid cells: 2.6 nCPM
epididymal clear cells: 2 nCPM
epididymal efferent duct absorptive cells: 1.9 nCPM

Immune cell

basophil: 0 nTPM
classical monocyte: 0 nTPM
eosinophil: 0 nTPM
gdT-cell: 0 nTPM
intermediate monocyte: 0 nTPM
MAIT T-cell: 0 nTPM

Brain region

choroid plexus: 0.4 nTPM
medulla oblongata: 0.2 nTPM
basal ganglia: 0.1 nTPM
cerebellum: 0.1 nTPM
cerebral cortex: 0.1 nTPM
midbrain: 0.1 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): 1.06
gnomAD pLI: 0
gnomAD missense Z: 0.49
DepMap mean gene effect: 0.03
DepMap dependency class: selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 1% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Molecular functions

Cellular components

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of TBC1D21 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 TBC1D21 as an antibody target. Whether an autoantibody or antibody against TBC1D21 could matter depends on whether native TBC1D21 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

TBC1D21 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 TBC1D21 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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