Chemokines GPCR with

Wu B, Chien EYT, Mol CD et al (2010) Stmctures of the CXCR4 chemokine GPCR with small-molecule and cyclic peptide antagonists. Science 330 1066-1071... 

Figure 2.3 Multiple sequence alignment of representative members of the chemokine receptor family and the GPCRs with known 3-D structure. The N- and C-terminus are omitted and e2 is only shown from the disulfide-bonded cysteine to TM5. The lengths of the i2 loops of rhodopsin, 3i- and 32-adrenergic receptors and the A2A adenosine receptor are large and they are not shown for clarity. Highly...

Data from studies with other GPCRs have highlighted the importance of extracellular cysteines in ligand binding and the maintenance of the conformational integrity of the receptors. There are typically four conserved cysteine residues found on extracellular domains of chemokine receptors (see Figure 1 and Tables 2 and 3) one on the amino-terminus and one on each of the three extracellular loops. It is clear that the cysteines on extracellular loops 1 and 2 form a disulfide bond that is essential for the proper trafficking of the receptors... 

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