Redman C M, Russo D, Lee S
Laboratory of Membrane Biochemistry, Lindsley F. Kimball Research Institute, New York Blood Center, NY 10021, USA.
Baillieres Best Pract Res Clin Haematol. 1999 Dec;12(4):621-35. doi: 10.1053/beha.1999.0045.
The antigens of the Kell blood group system are carried on a 93 kDa type II glycoprotein encoded by a single gene on chromosome 7 at 7q33. XK is a 50.9 kDa protein that traverses the membrane ten times and derives from a single gene on the X chromosome at Xp21. A single disulphide bond, Kell Cys 72-XK Cys 347, links Kell to XK. The Kell component of the Kell/XK complex is important in transfusion medicine since it is a highly polymorphic protein, carrying over 23 different antigens, that can cause severe reactions if mismatched blood is transfused and in pregnant mothers antibodies to Kell may elicit serious fetal and neonatal anaemia. The different Kell phenotypes are all caused by base mutations leading to single amino acid substitutions. By contrast the XK component carries a single blood group antigen, termed Kx. The physiological functions of Kell and XK have not been fully elucidated but Kell is a zinc endopeptidase with endothelin-3-converting enzyme activity and XK has the structural characteristics of a membrane transporter. Lack of Kx, the McLeod phenotype, is associated with red cell acanthocytosis, elevated levels of serum creatine phosphokinase and late onset forms of muscular and neurological defects.
凯尔血型系统的抗原由位于7号染色体7q33上的单基因编码的一种93 kDa的II型糖蛋白携带。XK是一种50.9 kDa的蛋白质，跨膜十次，来源于X染色体Xp21上的单基因。一个二硫键，凯尔半胱氨酸72-XK半胱氨酸347，将凯尔与XK连接起来。凯尔/XK复合物中的凯尔成分在输血医学中很重要，因为它是一种高度多态性的蛋白质，携带超过23种不同的抗原，如果输入不匹配的血液会引起严重反应，并且在怀孕母亲中，针对凯尔的抗体可能引发严重的胎儿和新生儿贫血。不同的凯尔表型均由导致单个氨基酸取代的碱基突变引起。相比之下，XK成分携带一种单一的血型抗原，称为Kx。凯尔和XK的生理功能尚未完全阐明，但凯尔是一种具有内皮素-3转换酶活性的锌内肽酶，而XK具有膜转运蛋白的结构特征。缺乏Kx（麦克劳德表型）与红细胞棘形红细胞增多症、血清肌酸磷酸激酶水平升高以及迟发性肌肉和神经缺陷有关。
