This locus controls the synthesis of the Kell blood group 'precursor substance' (Kx). Mutations in this gene have been associated with McLeod syndrome, an X-linked, recessive disorder characterized by abnormalities in the neuromuscular and hematopoietic systems. The encoded protein has structural characteristics of prokaryotic and eukaryotic membrane transport proteins. [provid... See more...

Aliases for XK Gene

Aliases for XK Gene

  • X-Linked Kx Blood Group 2 3 5
  • Kx Antigen 2 3 4
  • XKR1 2 3 4
  • XK, Kell Blood Group Complex Subunit (McLeod Syndrome) 2 3
  • Kell Blood Group Precursor (McLeod Phenotype) 2 3
  • Membrane Transport Protein XK 3 4
  • Kell Complex 37 KDa Component 3 4
  • XK-Related Protein 1 3 4
  • X1k 2 3
  • Truncated X-Linked Kx Blood Group 3
  • Kx Blood Group Antigen 3
  • Neuroacanthocytosis 2
  • Neurocanthocytosis 2
  • McLeod Syndrome 2
  • XRG1 4
  • NAC 3
  • KX 3
  • NA 3
  • XK 5
  • Kx 2

External Ids for XK Gene

Previous HGNC Symbols for XK Gene

  • NA
  • NAC

Previous GeneCards Identifiers for XK Gene

  • GC0XP035650
  • GC0XP035832
  • GC0XP036389
  • GC0XP036576
  • GC0XP036575
  • GC0XP037301
  • GC0XP037430
  • GC0XP037545
  • GC0XP035290

Summaries for XK Gene

Entrez Gene Summary for XK Gene

  • This locus controls the synthesis of the Kell blood group 'precursor substance' (Kx). Mutations in this gene have been associated with McLeod syndrome, an X-linked, recessive disorder characterized by abnormalities in the neuromuscular and hematopoietic systems. The encoded protein has structural characteristics of prokaryotic and eukaryotic membrane transport proteins. [provided by RefSeq, Jul 2008]

GeneCards Summary for XK Gene

XK (X-Linked Kx Blood Group) is a Protein Coding gene. Diseases associated with XK include Mcleod Syndrome and Choreoacanthocytosis. Among its related pathways are Signaling by GPCR and Peptide ligand-binding receptors. Gene Ontology (GO) annotations related to this gene include transporter activity. An important paralog of this gene is XKRX.

UniProtKB/Swiss-Prot Summary for XK Gene

  • May be involved in sodium-dependent transport of neutral amino acids or oligopeptides.

No data available for CIViC Summary , Tocris Summary , Gene Wiki entry , PharmGKB "VIP" Summary , Rfam classification and piRNA Summary for XK Gene

Genomics for XK Gene

GeneHancer (GH) Regulatory Elements Pubs

Promoters and enhancers for XK Gene
GeneHancer (GH) Identifier GH Type GH
GH Sources Gene Association Score Total Score TSS distance (kb) Number of Genes Away Size (kb) Transcription Factor
Binding Sites
Gene Targets
GH0XJ037684 Promoter/Enhancer 1.9 EPDnew Ensembl ENCODE CraniofacialAtlas 613.1 +0.1 108 3.5 KDM1A ZNF692 ZSCAN4 POLR2A ZNF24 ZNF600 ZFX SCRT2 NRF1 MGA XK LANCL3 H2AL1SP CYBB ENSG00000250349
GH0XJ037731 Promoter 0.3 EPDnew 600.3 +46.0 46002 0.1 XK Hsa-Mir-576_3p-003 piR-44253-023 CYBB ENSG00000250349
GH0XJ037780 Promoter/Enhancer 1.8 EPDnew FANTOM5 Ensembl ENCODE dbSUPER 12.2 +98.0 97993 9 IKZF2 POLR2A TRIM22 EED ARID3A ELK1 DPF2 ESR1 BCLAF1 ARNT CYBB XK lnc-CYBB-2 piR-38352-595 DYNLT3 ENSG00000250349
GH0XJ037753 Enhancer 1.4 FANTOM5 Ensembl ENCODE dbSUPER 12.3 +73.8 73815 17.8 SP1 ETV6 IKZF2 SOX6 EED ZNF766 DPF2 RUNX3 ZNF316 BCLAF1 CYBB XK piR-44253-023 Hsa-Mir-576_3p-003 ENSG00000250349
GH0XJ037746 Enhancer 1.2 FANTOM5 ENCODE dbSUPER 12.5 +60.7 60736 1.5 CTCF ZNF143 ZIC2 REST IKZF2 RCOR1 TRIM22 YY1 RELA EED XK CYBB piR-44253-023 Hsa-Mir-576_3p-003 ENSG00000250349
- Elite GeneHancer and/or Elite GeneHancer-gene association Download GeneHancer data from 2017 publication | Request up-to-date GeneHancer data (full dataset)

GeneHancers around XK on the GeneHancer Hub at the UCSC Golden Path

Cistromic (ChIP-Seq) regulation report from SPP (The Signaling Pathways Project) for XK

Top Transcription factor binding sites by QIAGEN in the XK gene promoter:
  • Nkx2-5
  • STAT1
  • STAT1alpha
  • STAT1beta
  • STAT2
  • STAT3
  • STAT4
  • STAT5A
  • STAT5B

Genomic Locations for XK Gene

Genomic Locations for XK Gene
46,445 bases
Plus strand
46,372 bases
Plus strand

Genomic View for XK Gene

Genes around XK on UCSC Golden Path with GeneCards custom track

Cytogenetic band:
XK Gene in genomic location: bands according to Ensembl, locations according to GeneLoc (and/or Entrez Gene and/or Ensembl if different)
Genomic Location for XK Gene
GeneLoc Logo Genomic Neighborhood Exon StructureGene Density

RefSeq DNA sequence for XK Gene

Proteins for XK Gene

  • Protein details for XK Gene (UniProtKB/Swiss-Prot)

    Protein Symbol:
    Recommended name:
    Membrane transport protein XK
    Protein Accession:
    Secondary Accessions:
    • Q4TTN6
    • Q8IUK6
    • Q9UC77

    Protein attributes for XK Gene

    444 amino acids
    Molecular mass:
    50902 Da
    Quaternary structure:
    • Heterodimer with Kell; disulfide-linked.

neXtProt entry for XK Gene

Post-translational modifications for XK Gene

Other Protein References for XK Gene

ENSEMBL proteins:
REFSEQ proteins:

No data available for DME Specific Peptides for XK Gene

Domains & Families for XK Gene

Gene Families for XK Gene

Human Protein Atlas (HPA):
  • Blood group antigen proteins
  • Disease related genes
  • Potential drug targets
  • Predicted membrane proteins
  • Transporters

Protein Domains for XK Gene


Suggested Antigen Peptide Sequences for XK Gene

GenScript: Design optimal peptide antigens:
  • XK protein (Q2Z218_HUMAN)
  • XK-related protein 1 (XK_HUMAN)

Graphical View of Domain Structure for InterPro Entry



  • Belongs to the XK family.
  • Belongs to the XK family.
genes like me logo Genes that share domains with XK: view

Function for XK Gene

Molecular function for XK Gene

UniProtKB/Swiss-Prot Function:
May be involved in sodium-dependent transport of neutral amino acids or oligopeptides.

Phenotypes From GWAS Catalog for XK Gene

Gene Ontology (GO) - Molecular Function for XK Gene

GO ID Qualified GO term Evidence PubMed IDs
GO:0005215 transporter activity TAS 8004674
GO:0005515 protein binding IPI 7737196
genes like me logo Genes that share ontologies with XK: view
genes like me logo Genes that share phenotypes with XK: view

Human Phenotype Ontology for XK Gene

HPO Id HPO Name Alternative Ids Definition Synonyms

Animal Models for XK Gene

MGI Knock Outs for XK:
  • Xk Xk<tm1Ariv>
  • Xk Xk<tm1b(KOMP)Mbp>

No data available for Enzyme Numbers (IUBMB) , Transcription Factor Targets and HOMER Transcription for XK Gene

Localization for XK Gene

Subcellular locations from UniProtKB/Swiss-Prot for XK Gene

Membrane. Multi-pass membrane protein.

Subcellular locations from

Extracellular space Cytosol Plasma membrane Cytoskeleton Lysosome Endosome Peroxisome ER Golgi Apparatus Nucleus Mitochondrion 0 1 2 3 4 5 Confidence
COMPARTMENTS Subcellular localization image for XK gene
Compartment Confidence
plasma membrane 5
mitochondrion 3
nucleus 2
extracellular 1
cytoskeleton 1
endoplasmic reticulum 1
endosome 1
cytosol 1
golgi apparatus 1

Subcellular locations from the

Human Protein Atlas (HPA)
  • Mitochondria (2)
  • Nucleoplasm (2)
  • Vesicles (2)
See all subcellular structures

Gene Ontology (GO) - Cellular Components for XK Gene

GO ID Qualified GO term Evidence PubMed IDs
GO:0005623 cell IEA --
GO:0005886 plasma membrane TAS --
GO:0016020 membrane IEA --
GO:0016021 integral component of membrane TAS 9647734
genes like me logo Genes that share ontologies with XK: view

Pathways & Interactions for XK Gene

genes like me logo Genes that share pathways with XK: view

Gene Ontology (GO) - Biological Process for XK Gene

GO ID Qualified GO term Evidence PubMed IDs
GO:0006865 amino acid transport IEA --
GO:0006874 cellular calcium ion homeostasis IEA --
GO:0008361 regulation of cell size IEA --
GO:0010961 cellular magnesium ion homeostasis IEA --
GO:0031133 regulation of axon diameter IEA --
genes like me logo Genes that share ontologies with XK: view

No data available for SIGNOR curated interactions for XK Gene

Drugs & Compounds for XK Gene

(22) Drugs for XK Gene - From: DrugBank and Novoseek

Name Status Disease Links Group Role Mechanism of Action Clinical Trials
Oseltamivir Approved Pharma Target, inhibitor 134
Peramivir Approved, Investigational Pharma Target, Target, Target 16
Zanamivir Approved, Investigational Pharma Target, Target, inhibitor 24
(2R,4S,5R,6R)-5-Acetamido-4-amino-6-(diethylcarbamoyl)oxane-2-carboxylic acid Experimental Pharma Target 0
1-[4-Carboxy-2-(3-Pentylamino)Phenyl]-5,5'-Di(Hydroxymethyl)Pyrrolidin-2-One Experimental Pharma Target 0

(1) Additional Compounds for XK Gene - From: HMDB

Name Synonyms Role CAS Number PubChem IDs PubMed IDs
  • Na(+)
  • Na+
  • SODIUM ion
genes like me logo Genes that share compounds with XK: view

Transcripts for XK Gene

mRNA/cDNA for XK Gene

3 NCBI additional mRNA sequence :
1 Ensembl transcripts including schematic representations, and UCSC links to gene/alias where relevant :

Alternative Splicing Database (ASD) splice patterns (SP) for XK Gene

No ASD Table

Relevant External Links for XK Gene

GeneLoc Exon Structure for

Expression for XK Gene

mRNA expression in normal human tissues from GTEx, Illumina, BioGPS, and SAGE for XK Gene

mRNA expression in embryonic tissues and stem cells from LifeMap Discovery

Protein differential expression in normal tissues from HIPED for XK Gene

This gene is overexpressed in Peripheral blood mononuclear cells (66.5).

Integrated Proteomics: protein expression in normal tissues and cell lines from ProteomicsDB and MOPED for XK Gene

Protein tissue co-expression partners for XK Gene

Transcriptomic regulation report from SPP (The Signaling Pathways Project) for XK

SOURCE GeneReport for Unigene cluster for XK Gene:


mRNA Expression by UniProt/SwissProt for XK Gene:

Tissue specificity: High levels in skeletal muscle, heart, brain, and pancreas; low levels in placenta, lung, liver, and kidney.

Evidence on tissue expression from TISSUES for XK Gene

  • Blood(3.1)
  • Nervous system(2.6)
  • Muscle(2.4)
  • Skin(2.1)
  • Heart(2)

Phenotype-based relationships between genes and organs from Gene ORGANizer for XK Gene

Germ Layers:
  • ectoderm
  • mesoderm
  • cardiovascular
  • nervous
  • skeletal muscle
Head and neck:
  • brain
  • ear
  • head
  • heart
  • heart valve
genes like me logo Genes that share expression patterns with XK: view

Primer Products

No data available for mRNA differential expression in normal tissues for XK Gene

Orthologs for XK Gene

This gene was present in the common ancestor of chordates.

Orthologs for XK Gene

Organism Taxonomy Gene Similarity Type Details
(Pan troglodytes)
Mammalia XK 30 31
  • 99.55 (n)
(Canis familiaris)
Mammalia XK 30 31
  • 86.64 (n)
(Mus musculus)
Mammalia Xk 30 17 31
  • 82.66 (n)
(Rattus norvegicus)
Mammalia Xk 30
  • 81.94 (n)
(Bos Taurus)
Mammalia XK 30 31
  • 81.4 (n)
(Monodelphis domestica)
Mammalia XK 31
  • 74 (a)
(Ornithorhynchus anatinus)
Mammalia -- 31
  • 70 (a)
-- 31
  • 68 (a)
(Gallus gallus)
Aves XK 30 31
  • 72.38 (n)
(Anolis carolinensis)
Reptilia XK 31
  • 57 (a)
Tropical Clawed Frog
(Silurana tropicalis)
Amphibia xk 30
  • 69.37 (n)
Str.1221 30
(Danio rerio)
Actinopterygii xk 30 31
  • 63.99 (n)
Species where no ortholog for XK was found in the sources mined by GeneCards:
  • A. gosspyii yeast (Eremothecium gossypii)
  • Actinobacteria (Mycobacterium tuberculosis)
  • African clawed frog (Xenopus laevis)
  • African malaria mosquito (Anopheles gambiae)
  • Alicante grape (Vitis vinifera)
  • Alpha proteobacteria (Wolbachia pipientis)
  • Amoeba (Dictyostelium discoideum)
  • Archea (Pyrococcus horikoshii)
  • Baker's yeast (Saccharomyces cerevisiae)
  • Barley (Hordeum vulgare)
  • Beta proteobacteria (Neisseria meningitidis)
  • Bread mold (Neurospora crassa)
  • Chromalveolata (Phytophthora infestans)
  • Common water flea (Daphnia pulex)
  • Corn (Zea mays)
  • E. coli (Escherichia coli)
  • Filamentous fungi (Aspergillus nidulans)
  • Firmicute Bacteria (Streptococcus pneumoniae)
  • Fission Yeast (Schizosaccharomyces pombe)
  • Fruit Fly (Drosophila melanogaster)
  • Green Algae (Chlamydomonas reinhardtii)
  • Honey Bee (Apis mellifera)
  • K. Lactis Yeast (Kluyveromyces lactis)
  • Loblloly Pine (Pinus taeda)
  • Malaria Parasite (Plasmodium falciparum)
  • Medicago Trunc (Medicago Truncatula)
  • Moss (Physcomitrella patens)
  • Orangutan (Pongo pygmaeus)
  • Pig (Sus scrofa)
  • Rainbow Trout (Oncorhynchus mykiss)
  • Rice (Oryza sativa)
  • Rice Blast Fungus (Magnaporthe grisea)
  • Schistosome Parasite (Schistosoma mansoni)
  • Sea Anemone (Nematostella vectensis)
  • Sea Vase (Ciona intestinalis)
  • Sea Squirt (Ciona savignyi)
  • Sea Urchin (Strongylocentrotus purpuratus)
  • Sorghum (Sorghum bicolor)
  • Soybean (Glycine max)
  • Stem Rust Fungus (Puccinia graminis)
  • Sugarcane (Saccharum officinarum)
  • Thale Cress (Arabidopsis thaliana)
  • Tomato (Lycopersicon esculentum)
  • Toxoplasmosis (Toxoplasma gondii)
  • Trichoplax (Trichoplax adhaerens)
  • Wheat (Triticum aestivum)
  • Worm (Caenorhabditis elegans)

Evolution for XK Gene

Gene Tree for XK (if available)
Gene Tree for XK (if available)
Evolutionary constrained regions (ECRs) for XK: view image

Paralogs for XK Gene

Paralogs for XK Gene

(2) SIMAP similar genes for XK Gene using alignment to 2 proteins:

  • Q2Z218_HUMAN
genes like me logo Genes that share paralogs with XK: view

Variants for XK Gene

Polymorphic Variants from UniProtKB/Swiss-Prot for XK Gene

XK is responsible for the Kx blood group system.

Sequence variations, with clinical significance, from ClinVar and Humsavar, with links to dbSNP for XK Gene

SNP ID Clinical significance and condition Chr 0X pos Variation AA Info Type
695327 Benign: not provided 37,686,111(+) C/T SYNONYMOUS_VARIANT
695501 Benign: not provided 37,728,348(+) G/A SYNONYMOUS_VARIANT
695682 Benign: not provided 37,728,235(+) T/G MISSENSE_VARIANT
742021 Benign: not provided 37,694,532(+) C/T SYNONYMOUS_VARIANT
744635 Likely Benign: not provided 37,694,457(+) G/T SYNONYMOUS_VARIANT

Additional dbSNP identifiers (rs#s) for XK Gene

Variation tolerance for XK Gene

Residual Variation Intolerance Score: 25.7% of all genes are more intolerant (likely to be disease-causing)
Gene Damage Index Score: 0.12; 2.70% of all genes are more intolerant (likely to be disease-causing)

Additional Variant Information for XK Gene

Blood Group Antigen Gene Mutation Database (BGMUT)
Blood Group System
Human Gene Mutation Database (HGMD)
SNPedia medical, phenotypic, and genealogical associations of SNPs for

SNP Genotyping and Copy Number Assay Products

No data available for Structural Variations from Database of Genomic Variants (DGV) for XK Gene

Disorders for XK Gene

MalaCards: The human disease database

(23) MalaCards diseases for XK Gene - From: UniProtKB/Swiss-Prot, OMIM, ClinVar, GTR, Orphanet, DISEASES, Novoseek, and GeneCards

Disorder Aliases PubMed IDs
mcleod syndrome
  • mclds
  • chac
hyperlucent lung
  • lung, hyperlucent
chronic granulomatous disease
  • granulomatous disease, chronic, x-linked
chorea gravidarum
- elite association - COSMIC cancer census association via MalaCards
Search XK in MalaCards View complete list of genes associated with diseases


  • McLeod syndrome (MLS) [MIM:300842]: A multisystem disorder characterized by the absence of red blood cell Kx antigen, weak expression of Kell red blood cell antigens, acanthocytosis, and compensated hemolysis. Most carriers of this McLeod blood group phenotype have acanthocytosis and elevated serum creatine kinase levels and are prone to develop a severe neurologic disorder resembling Huntington disease. Additional symptoms include generalized seizures, neuromuscular symptoms leading to weakness and atrophy, and cardiomyopathy mainly manifesting with atrial fibrillation, malignant arrhythmias, and dilated cardiomyopathy. {ECO:0000269 PubMed:11761473, ECO:0000269 PubMed:11961232, ECO:0000269 PubMed:12823753}. Note=The disease is caused by mutations affecting the gene represented in this entry.

Additional Disease Information for XK

Genetic Association Database
Human Genome Epidemiology Navigator
ATLAS of Genetics and Cytogenetics in Oncology and Haematology
Open Targets Platform
genes like me logo Genes that share disorders with XK: view

No data available for Genatlas for XK Gene

Publications for XK Gene

  1. McLeod phenotype associated with a XK missense mutation without hematologic, neuromuscular, or cerebral involvement. (PMID: 12823753) Jung HH … Frey BM (Transfusion 2003) 3 4 23 41
  2. McLeod neuroacanthocytosis: genotype and phenotype. (PMID: 11761473) Danek A … Monaco AP (Annals of neurology 2001) 2 3 4 23
  3. Association of XK and Kell blood group proteins. (PMID: 9593744) Russo D … Lee S (The Journal of biological chemistry 1998) 3 4 23
  4. Purification and partial characterization of the erythrocyte Kx protein deficient in McLeod patients. (PMID: 7737196) Khamlichi S … Bertrand O (European journal of biochemistry 1995) 3 4 23
  5. Isolation of the gene for McLeod syndrome that encodes a novel membrane transport protein. (PMID: 8004674) Ho M … Monaco AP (Cell 1994) 2 3 4

Products for XK Gene