Figure 44

Schematic representation of the interactions of sickle red cells. Sickle red cells (dark circles) traverse the microcirculation, releasing oxygen from oxyhemoglobin, and change into deoxyhemoglobin (light circles). Deoxygenation of hemoglobin S induces a change in conformation in which the |3 sub-units move away from each other. The hydrophobic patch at the site of the |3g where the valine replacement has occurred (shown as a projection) can bind to a complementary hydrophobic site of the |3g valine replacement (shown as an indentation). This mechanism is important for the formation of a polymer (see Fig. 4-4). The diagram to the right shows the assembly of deoxyhemoglo-bin S into a helical 14-strand fiber: a polymer is formed (see Fig. 4-5). As the deoxyhemoglobin S polymerizes and fibers align, the erythrocyte is transformed into a "sickle" shape, observed at the bottom by scanning electron micrography. (Adapted from Bunn [4]; with permission).

0 0

Post a comment