Seroatlas · Human Serome Atlas

XKR4

XK-related protein 4

Also known as: KIAA1889, XKR4_HUMAN

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

Protein identityUniProt · HPA

UniProt accession: Q5GH76
Gene: XKR4
Ensembl: ENSG00000206579
Chromosome: 8
Canonical length: 650 aa
Protein class: Predicted membrane proteins, Transporters
Subcellular location: Nucleoli,Golgi apparatus,Vesicles
Quaternary structure: Homodimer

OverviewNCBI Gene

Enables phospholipid scramblase activity. Involved in phosphatidylserine exposure on apoptotic cell surface. Predicted to be located in membrane. Predicted to be active in plasma membrane. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

650 residues, UniProt reviewed canonical sequence.

>Q5GH76|XKR4
     1  MAAKSDGRLK MKKSSDVAFT PLQNSDHSGS VQGLAPGLPS GSGAEDEEAA GGGCCPDGGG
    61  CSRCCCCCAG SGGSAGSGGS GGVAGPGGGG AGSAALCLRL GREQRRYSLW DCLWILAAVA
   121  VYFADVGTDV WLAVDYYLRG QRWWFGLTLF FVVLGSLSVQ VFSFRWFVHD FSTEDSATAA
   181  AASSCPQPGA DCKTVVGGGS AAGEGEARPS TPQRQASNAS KSNIAAANSG SNSSGATRAS
   241  GKHRSASCSF CIWLLQSLIH ILQLGQIWRY FHTIYLGIRS RQSGENDRWR FYWKMVYEYA
   301  DVSMLHLLAT FLESAPQLVL QLCIIVQTHS LQALQGFTAA ASLVSLAWAL ASYQKALRDS
   361  RDDKKPISYM AVIIQFCWHF FTIAARVITF ALFASVFQLY FGIFIVLHWC IMTFWIVHCE
   421  TEFCITKWEE IVFDMVVGII YIFSWFNVKE GRTRCRLFIY YFVILLENTA LSALWYLYKA
   481  PQIADAFAIP ALCVVFSSFL TGVVFMLMYY AFFHPNGPRF GQSPSCACED PAAAFTLPPD
   541  VATSTLRSIS NNRSVVSDRD QKFAERDGCV PVFQVRPTAP STPSSRPPRI EESVIKIDLF
   601  RNRYPAWERH VLDRSLRKAI LAFECSPSPP RLQYKDDALI QERLEYETTL

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against XKR4 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: Cell surface
Secreted: No
Transmembrane segments: 10
Mean surface accessibility (rSASA): 0.43
Highest tissue expression: 2.7 nTPM

Expression across tissuesHPA

Tissue

cerebral cortex: 2.7 nTPM
colon: 1.7 nTPM
hypothalamus: 1 nTPM
amygdala: 0.9 nTPM
basal ganglia: 0.8 nTPM
cerebellum: 0.8 nTPM

Single-cell type

oligodendrocyte progenitor cells: 1,033 nCPM
schwann cells: 799 nCPM
lactotrophs: 776 nCPM
brain inhibitory neurons: 763 nCPM
retinal amacrine cells: 624 nCPM
gonadotrophs: 616 nCPM

Immune cell

basophil: 0.4 nTPM
neutrophil: 0.1 nTPM
classical monocyte: 0 nTPM
eosinophil: 0 nTPM
gdT-cell: 0 nTPM
intermediate monocyte: 0 nTPM

Brain region

cerebral cortex: 32 nTPM
basal ganglia: 32 nTPM
thalamus: 27 nTPM
amygdala: 27 nTPM
hypothalamus: 20 nTPM
white matter: 18 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): 0.19
gnomAD pLI: 1
gnomAD missense Z: 1.64
DepMap mean gene effect: -0.05
DepMap dependency class: selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 3% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Cellular components

plasma membrane

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of XKR4 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

XRCC4

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads XKR4 as an antibody target. Whether an autoantibody or antibody against XKR4 could matter depends on whether native XKR4 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

XKR4 is annotated at the cell surface, where native XKR4 is exposed to circulating antibodies and is a prime autoantibody target that could block, deplete, or overstimulate it.

Annotation status

The present source text does not explicitly label XKR4 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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