Abraham then brought the project to Harrison, who had mentored the young scientist in 2004 as part of HHMI's Exceptional Research Opportunities Program (EXROP), which places undergraduate students from disadvantaged backgrounds in the laboratories of HHMI investigators and HHMI professors. The pairing was fortuitous. In Choe's laboratory, Abraham had developed methods to produce the Machupo virus surface protein, which links to the human transferrin receptor. Meanwhile, Harrison had stocks of purified transferrin receptor because he had previously worked to image the molecule and understood its molecular structure.
Together, the pair made batches of the Machupo surface protein bound to the transferrin receptor and then set about creating an image showing how the two molecules connected. They used x-ray crystallography, a technique in which protein crystals are bombarded with x-ray beams. As the x-rays pass through and bounce off of atoms in the crystal, they produce a diffraction pattern, which can then be analyzed to determine the three-dimensional shape of the protein. After a data collection trip to the powerful x-ray beam at Argonne National Laboratory in Illinois, Abraham and Harrison were able to examine the atomic structure of the Machupo surface protein attached to the transferrin receptor.
The images show that the Machupo surface protein binds to the transferrin receptor in a surprising wayusing a loop called the apical domain. The biological function of this loop in hu
|Contact: Andrea Widener|
Howard Hughes Medical Institute