XK is a protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 found on human red blood cells and other tissues which is responsible for the Kx antigen

Antigen

An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...

 which helps determine a person's blood type

Blood type

A blood type is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells . These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system...

.

Clinical significance

The Kx antigen plays a role in matching blood for blood transfusion

Blood transfusion

Blood transfusion is the process of receiving blood products into one's circulation intravenously. Transfusions are used in a variety of medical conditions to replace lost components of the blood...

s.

Mutation of XK protein may lead to McLeod syndrome

McLeod syndrome

McLeod syndrome is a genetic disorder that may affect the blood, brain, peripheral nerves, muscle and heart. It is caused by a variety of recessively-inherited mutations in the XK gene on the X chromosome...

, a multi-system disorder characterized by hemolytic anemia

Hemolytic anemia

Hemolytic anemia is a form of anemia due to hemolysis, the abnormal breakdown of red blood cells , either in the blood vessels or elsewhere in the human body . It has numerous possible causes, ranging from relatively harmless to life-threatening...

, myopathy

Myopathy

In medicine, a myopathy is a muscular disease in which the muscle fibers do not function for any one of many reasons, resulting in muscular weakness. "Myopathy" simply means muscle disease...

, acanthocytosis

Acanthocyte

Acanthocyte, in human biology and medicine, refers to a form of red blood cell that are spiked, or possess various abnormal thorny projections. Acanthocytosis is the condition with acanthocyte-like red blood cells....

, and chorea.
XK is located on the X chromosome

X chromosome

The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...

 and absence of the XK protein is an X-linked disease

Sex linkage

Sex linkage is the phenotypic expression of an allele related to the chromosomal sex of the individual. This mode of inheritance is in contrast to the inheritance of traits on autosomal chromosomes, where both sexes have the same probability of inheritance...

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External links

• GeneReviews/NCBI/NIH/UW entry on McLeod Neuroacanthocytosis Syndrome
• XK at BGMUT
  BGMUT
  The BGMUT Database documents allelic variations in the genes encoding for human blood group systems. It was set up in 1999 through an initiative of the Human Genome Variation Society . Since 2006, it has been a part of the dbRBC resource of NCBI at the NIH...
  
   Blood Group Antigen Gene Mutation Database at NCBI
  National Center for Biotechnology Information
  The National Center for Biotechnology Information is part of the United States National Library of Medicine , a branch of the National Institutes of Health. The NCBI is located in Bethesda, Maryland and was founded in 1988 through legislation sponsored by Senator Claude Pepper...
  
  , NIH