Figure 42

Respiratory movement of a hemoglobin molecule. From a functional point of view the so-called respiratory movement of the hemoglobin molecule is of great importance. When the four oxygen atoms bind to oxyhemoglobin, the firmly bound aj-Pj and aj-^2 move away from each other slightly. After full oxygenation the heme groups of the P chains are 7 Â closer to each other (R configuration). After deoxy-genation the opposite occurs (T configuration). This "respiratory movement" (R indicates the relaxed and T the tense configuration) is of great importance in our understanding of the pathogenesis of sick-ling: polymerization occurs when the T configuration takes place. (Adapted from Dickerson and Geis [7]; with permission.)

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