Crystal structures of agonist and antagonist mimetics with erythropoietin receptor

A suprising development in the cytokine receptor field has been the recent discovery of a short 20-residue peptide agonist that mimics the biological activity of the erythropoietin (EPO) natural hormone (Wrighton et al., 1996). The crystal structure determination of the EPO receptor with the agonist peptide showed that Ihe peptide itself dimerizes and causes a symmetric dimerization of the receptor (Livnah et al.. 1996). The dimer configuration is undoubtedly different to that when EPO binds and suggests that more than one mode of dimerization can lead to or produce a biological response. The peptide contacts only a relatively small portion of the surface of the EPOR that corresponds to the "hot spot" or functional epitope on a receptor surface that was identified for human growth hormone receptor (Clackson & Wells, 1996).