High Quality Content by WIKIPEDIA articles! The erythropoietin receptor (EpoR) is a protein that in humans is encoded by the EPOR gene. EpoR is a 59 kDa peptide and is a member of the cytokine receptor family. EpoR pre-exists as dimers which upon binding of a 34 kDa ligand erythropoietin (Epo), changes its homodimerized state. These conformational changes result in the autophosphorylation of Jak2 kinases that are pre-associated with the receptor (i.e., EpoR does not possess intrinsic kinase activity and depends on Jak2 activity). At present, the most well-established function of EpoR is to rescue erythroid (red blood cell) progenitors from apoptosis.