| STRUCTURE |
Protein stabilizes -hemoglobin © NATURE 2005 Researchers have determined how a major component of hemoglobin--the protein complex that carries oxygen to tissues and organs--retains its structure and stability. In the body, hemoglobin is assembled from - and -hemoglobin subunits. Although -hemoglobin is relatively stable, -hemoglobin is not. In fact, -hemoglobin can unfold and release heme, leading to serious blood disorders. Thus, it's necessary to stabilize -hemoglobin before it is incorporated into hemoglobin. This function is filled by -hemoglobin-stabilizing protein (AHSP). Princeton University molecular biologist Yigong Shi and his colleagues have now obtained a crystal structure of the -hemoglobin/AHSP complex (shown) that reveals how the protein stabilizes -hemoglobin (Nature 2005, 435, 697). The researchers report that binding to AHSP causes a-hemoglobin to "undergo drastic structural rearrangements." As a result, the heme iron (large red ball) assumes a nonreactive ferric form in which it is coordinated by two histidines of -hemoglobin, in addition to the four nitrogen atoms on heme's porphyrin ring. |
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