Expression of recombinant Emp. (A) Full-length (Emp-1) and truncated (Emp-2) human Emp were expressed as glutathione S-transferase (GST) fusion proteins in bacteria. Cell lysates of bacteria transformed with GST-Emp-1 and -2 constructs (lanes 1 and 2, respectively) were separated by SDS-PAGE and stained directly with Coomassie blue or transferred to nitrocellulose, probed with radiolabeled erythroblasts followed by autoradiography, or probed with affinity-purified anti-Emp antibody and immunoreactive bands were detected by ECL. (B) Full-length (Emp-1) and truncated (Emp-2) human Emp were expressed in COS-7 cells as fusion proteins containing HA tag at the C-terminus. Transfected and nontransfected COS-7 cells were either metabolically labeled with [³⁵S]methionine or surface labeled with [¹²⁵I], followed by immunoprecipitation with anti-HA tag antibodies. Autoradiographs of the immunoprecipitates are shown. The position of the molecular weight standards is indicated on the left.