Skip navigation

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

URL of this page:

XK gene

X-linked Kx blood group antigen, Kell and VPS13A binding protein

Normal Function

The XK gene provides instructions for producing a protein that is found in various tissues of the body, particularly the brain, muscle, and heart. This protein is also present on the surface of red blood cells and carries a molecule known as the Kx blood group antigen. Blood group antigens are found on the surface of red blood cells and determine a number of blood types. When blood cells with unfamiliar antigens enter the bloodstream, the body's immune system recognizes the cells as foreign and may trigger an immune reaction that destroys the foreign blood cells.

The function of the XK protein is unclear; researchers believe that it might play a role in transporting substances into and out of cells. On red blood cells, the XK protein attaches to another blood group protein, the Kell protein. The function of this blood group complex is unknown.

Health Conditions Related to Genetic Changes

McLeod neuroacanthocytosis syndrome

Approximately 30 mutations in the XK gene have been found to cause McLeod neuroacanthocytosis syndrome. Most of these mutations lead to the production of an abnormally short, nonfunctional XK protein or cause no XK protein to be produced at all. Missing or abnormal XK protein also affects another blood group antigen, the Kell protein, causing it to be less prevalent on the surface of red blood cells. How mutations in the XK gene cause the misshapen red blood cells and movement problems characteristic of McLeod neuroacanthocytosis syndrome is unknown.

More About This Health Condition

Other Names for This Gene

  • Kell blood group precursor (McLeod phenotype)
  • KX
  • Kx antigen
  • membrane transport protein XK
  • X-linked Kx blood group (McLeod syndrome)
  • X1k
  • XK, Kell blood group complex subunit (McLeod syndrome)
  • XK-related protein 1
  • XKR1

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases


  • Claperon A, Hattab C, Armand V, Trottier S, Bertrand O, Ouimet T. The Kell and XK proteins of the Kell blood group are not co-expressed in the central nervous system. Brain Res. 2007 May 25;1147:12-24. doi: 10.1016/j.brainres.2007.01.106. Epub 2007 Feb 2. Citation on PubMed
  • Danek A, Rubio JP, Rampoldi L, Ho M, Dobson-Stone C, Tison F, Symmans WA, Oechsner M, Kalckreuth W, Watt JM, Corbett AJ, Hamdalla HH, Marshall AG, Sutton I, Dotti MT, Malandrini A, Walker RH, Daniels G, Monaco AP. McLeod neuroacanthocytosis: genotype and phenotype. Ann Neurol. 2001 Dec;50(6):755-64. doi: 10.1002/ana.10035. Citation on PubMed
  • Lee S. The value of DNA analysis for antigens of the Kell and Kx blood group systems. Transfusion. 2007 Jul;47(1 Suppl):32S-9S. doi: 10.1111/j.1537-2995.2007.01308.x. No abstract available. Citation on PubMed
  • Russo DC, Lee S, Reid ME, Redman CM. Point mutations causing the McLeod phenotype. Transfusion. 2002 Mar;42(3):287-93. doi: 10.1046/j.1537-2995.2002.00049.x. Citation on PubMed

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.