Subunit Structure of the Erythropoietin Receptor Analyzed By 1251-Epo Cross-Linking in Cells Expressing Wild-Type or Mutant Receptors

To analyze the structure of the murine erythropoietin receptor (EpoR), wild-type or mutant EpoR cDNAs were expressed in cell lines, and the proteins that cross-linked with '261-labeled erythropoietin (Epo) were analyzed by immunoprecipitation using an antibody against the intracellular region of the cloned EpoR. COS-7 cell transfectants expressing the wild-type EpoR showed two major cross-linked species of 145 and 1 10 Kd, both of which were recognized by the antibody against the cloned EpoR after denaturation under reducing conditions. Furthermore, a reduction in sizes of both cross-linked bands was observed in COS-7 transfectants expressing a mutant receptor with an internal deletion, thus indicating that both species contain the cloned EpoR. COS-7 cells expressing mutant receptors with