Abstract
A partial elucidation of the mechanism of a unique hemolytic system has been presented. This system involves the hemolysis of red cells by a protein factor isolated from rabbit erythrocytes in the presence of ATP, Mg 2+ and Na + or K +. The involvement of two discrete steps was indicated. The first concerned a binding of the hemolytic factor to the red cell membrane and required ATP, Mg 2+ and Na − or K −. This reaction could be monitored by a stroma-inhibition assay. The ADP-ATP exchange reaction of hemolytic factor indicated that a high-energy phosphorylated intermediate may interact with the red cell membrane. The second step in the process concerned the hemolysis of the red cells. This could be made to occur in an isolated, hemolytically active hemolytic factor-erythrocyte complex which did not require ATP, other cofactors or added hemolytic factor. The equilibrium of Na + and K + occurred down a concentration gradient followed by hemoglobin efflux. The hemolytic factor-erythrocyte complex could be separated from hemolytic factor binding to the red cell membrane by taking advantage of the occurrence of binding at pH 7.5 where hemolysis was inhibited. Hemolysis by the hemolytic factor-erythrocyte complex can also be completely inhibited by 1.0 mM N- ethylmalcimide . The overall hemolysis reaction was inhibited by increasing concentrations of Na +, K + and sucrose. The hemolytic factor-binding step was activated by Na + and K + while sucrose had no effect. ATP, a substrate for the binding step, was found to inhibit overall hemolysis and its component steps of hemolytic factor binding and hemolytic factor erythrocyte complex hemolysis at higher concentrations. ADP which was not required for hemolysis, inhibited in a manner similar to that of ATP. A comparison of the above inhibitory effects was made between the overall hemolytic reaction and its component parts and a scheme for the hemolytic process was presented.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Biomembranes
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