Kell Protein (KEL)

The KEL gene encodes a type II transmembrane glycoprotein that is the highly polymorphic Kell blood group antigen. The Kell glycoprotein links via a single disulfide bond to the XK membrane protein that carries the Kx antigen.

The encoded protein contains sequence and structural similarity to members of the neprilysin (M13) family of zinc endopeptidases. There are several alleles of the gene which creates Kell protein. Two such alleles, K₁ (Kell) and K₂ (Cellano), are the most common. The kell protein is tightly bound to a second protein, XK, by a disulfide bond. Absence of the XK protein (such as through genetic deletion), leads to marked reduction of the Kell antigens on the red blood cell surface. Absence of the Kell protein (K₀), however, does not affect the XK protein.