Structure of the transferrin receptor TfR1.

<p>The dimeric, butterfly-shaped protein TfR1 comprises three domains (colored yellow, red, and green in one protomer; the other protomer is shown in cyan). The receptor-binding domain of the Machupo virus GP1 protein (purple) is shown bound to the TfR1 apical domain. The purple and blue ovals illustrate the sites of Machupo GP1 and MMTV envelope surface (SU) protein binding, respectively, as well as the sites of positive selection. Reprinted with modification from <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001574#pbio.1001574-Abraham1" target="_blank">[12]</a>, with permission.