Interaction of sickle cell hemoglobin with erythrocyte membranes.

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Abstract
The interactions of Hb S with the [human] erythrocyte membrane were compared with the corresponding interactions of Hb A by measuring in both steady-state and kinetic experiments the quenching of the fluorescence of a probe embedded in erythrocyte membranes. Whereas Hb A could be dissociated from membranes, a fraction of Hb S was irreversibly bound even in the oxy state. DeoxyHb S interacted much more strongly with erythrocyte membranes than did deoxy-Hb A: a portion of the deoxyHb S was irreversibly bound, and the reversibly bound fraction of Hb S dissociated more slowly than did deoxyHb A. The binding of deoxyHb S may be a 2-step reaction in which the 1st step involves electrostatic interaction with band III erythrocyte membrane protein and the 2nd step involves a hydrophobic interaction with membrane lipids. The latter reaction reflects the greater hydrophobicity of Hb S. The unique interaction of Hb S with erythrocyte membranes may be important in the formation of irreversibly sickled cells.