Receptor superfamilies extracellular ligand binding domains

The biological effects of chemokines are mediated by the interaction of these soluble proteins with their specific receptors, which belong to the superfamily of seven-transmembrane G-protein-coupled receptors (see Chap. 2). Similar to the chemokines themselves, the number of novel chemokine receptors identified has expanded rapidly. To date, 11 CC, 6 CXC, 1 CX3C, and 1 C-chemokine receptors have been characterized (2). The extracellular domain consists of an NHj-terminus and three extracellular loops, which act in concert to bind to the chemokine ligand. The intracellular region is composed of three loops and the COOH-terminus, which transduce the chemokine signal and regulate expression of the receptor (2). 

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