Molecular characteristics of the transferrin-receptor complex of the rabbit reticulocyte.

A macromolecular complex of transferrin and a membrane component was isolated by gel filtration chromatography from Triton X-100-solubilized ghosts of reticulocytes previously incubated with 125I-labeled transferrin. This complex is believed to be transferrin specifically associated with its primary receptors. Following the procedures of Clark [14], the complex in Triton X-100 was found to behave as an asymmetric molecule with a molecular weight of approximately 250,000 and an axial ratio of 9:1. On SDS-poly-acrylamide gel electrophoresis the complex displays, in addition to transferrin, components of molecular weights 176,000 and 95,000, respectively. The larger component may be a dimer of the smaller. Each appears to crosslink, with dimethyl suberimidate, to transferrin. These results are compatible with the hypothesis that the transferrin receptor itself has a molecular weight near 175,000 and may be a dimer of two smaller components each of molecular weight near 95,000.