XK (protein)

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XK (protein)
Alt. symbolsXKR1, Kx, X1k
Other data
LocusChr. X p21.2-p21.1

XK (also known as Kell blood group precursor) is a protein found on human red blood cells and other tissues which is responsible for the Kx antigen which helps determine a person's blood type.

Clinical significance

The Kx antigen plays a role in matching blood for blood transfusions.

Mutation of XK protein may lead to McLeod syndrome,[1] a multi-system disorder characterized by hemolytic anemia, myopathy, acanthocytosis, and chorea.[2]

XK is located on the X chromosome (cytogenetic band Xp21.1) and absence of the XK protein is an X-linked disease.[3]


XK is a membrane transport protein of unknown action.[4]


  1. Arnaud L, Salachas F, Lucien N, et al. (March 2009). "Identification and characterization of a novel XK splice site mutation in a patient with McLeod syndrome". Transfusion. 49 (3): 479–84. doi:10.1111/j.1537-2995.2008.02003.x. PMID 19040496.
  2. Malandrini, A; Fabrizi, GM; Truschi, F; Di Pietro, G; Moschini, F; Bartalucci, P; Berti, G; Salvadori, C; et al. (1994). "Atypical McLeod syndrome manifested as X-linked chorea-acanthocytosis, neuromyopathy and dilated cardiomyopathy: report of a family". Journal of the Neurological Sciences. 124 (1): 89–94. doi:10.1016/0022-510X(94)90016-7. PMID 7931427.
  3. Ho, MF; Monaco, AP; Blonden, LA; Van Ommen, GJ; Affara, NA; Ferguson-Smith, MA; Lehrach, H (1992). "Fine mapping of the McLeod locus (XK) to a 150-380-kb region in Xp21". American Journal of Human Genetics. 50 (2): 317–30. PMC 1682457. PMID 1734714.
  4. Jung, HH; Russo, D; Redman, C; Brandner, S (2001). "Kell and XK immunohistochemistry in McLeod myopathy". Muscle & Nerve. 24 (10): 1346–51. doi:10.1002/mus.1154. PMID 11562915.

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