Seroatlas · Human Serome Atlas

XKR9

XK-related protein 9

Also known as: XKR9_HUMAN

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

Protein identityUniProt · HPA

UniProt accession: Q5GH70
Gene: XKR9
Ensembl: ENSG00000221947
Chromosome: 8
Canonical length: 373 aa
Protein class: Predicted membrane proteins, Transporters
Subcellular location: Mitochondria

OverviewNCBI Gene

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

Canonical amino-acid sequenceUniProt

373 residues, UniProt reviewed canonical sequence.

>Q5GH70|XKR9
     1  MKYTKQNFMM SVLGIIIYVT DLIVDIWVSV RFFHEGQYVF SALALSFMLF GTLVAQCFSY
    61  SWFKADLKKA GQESQHCFLL LHCLQGGVFT RYWFALKRGY HAAFKYDSNT SNFVEEQIDL
   121  HKEVIDRVTD LSMLRLFETY LEGCPQLILQ LYILLEHGQA NFSQYAAIMV SCCAISWSTV
   181  DYQVALRKSL PDKKLLNGLC PKITYLFYKL FTLLSWMLSV VLLLFLNVKI ALFLLLFLWL
   241  LGIIWAFKNN TQFCTCISME FLYRIVVGFI LIFTFFNIKG QNTKCPMSCY YIVRVLGTLG
   301  ILTVFWVCPL TIFNPDYFIP ISITIVLTLL LGILFLIVYY GSFHPNRSAE TKCDEIDGKP
   361  VLRECRMRYF LME

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against XKR9 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: 7
Mean surface accessibility (rSASA): 0.29
Highest tissue expression: 6.9 nTPM

Expression across tissuesHPA

Tissue

testis: 6.9 nTPM
small intestine: 5 nTPM
liver: 3.1 nTPM
duodenum: 2.5 nTPM
gallbladder: 2.1 nTPM
retina: 1.9 nTPM

Single-cell type

proximal tubule cells: 28 nCPM
papillary tip epithelial cells: 14 nCPM
tuft cells: 12 nCPM
loop of henle epithelial cells: 9.8 nCPM
distal convoluted tubule cells: 8.5 nCPM
renal connecting tubule cells: 7.2 nCPM

Immune cell

T-reg: 0.8 nTPM
naive CD4 T-cell: 0.5 nTPM
MAIT T-cell: 0.4 nTPM
memory CD4 T-cell: 0.4 nTPM
naive CD8 T-cell: 0.4 nTPM
basophil: 0.1 nTPM

Brain region

white matter: 7 nTPM
cerebral cortex: 6.9 nTPM
pons: 6 nTPM
medulla oblongata: 5.1 nTPM
thalamus: 4.6 nTPM
amygdala: 4.5 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): 1.56
gnomAD pLI: 0
gnomAD missense Z: -1.71
DepMap mean gene effect: -0.03
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

apoptotic process

Cellular components

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads XKR9 as an antibody target. Whether an autoantibody or antibody against XKR9 could matter depends on whether native XKR9 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

XKR9 is annotated at the cell surface, where native XKR9 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 XKR9 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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