Human hemoglobin (Hb), a tetrameric protein responsible for oxygen transport, is found in the highly reducing environment of RBCs.  Research has shown that extracellular Hb from hemolysis or transfusion of artificial blood can induce life threatening radical generating reactions. Thus, biological systems express proteins like Hp (found in blood plasma) or AHSP (present inside erythrocytes) which bind with either cell free Hb or the a-Hb in the erythrocytes to reduce these adverse effects. Our current ex vivo experiments show that Hp or AHSP when bound to cell free Hb or a-Hb respectively lower the reduction potential (E1/2) of these �complexed� systems  to a more negative value compared to the respective free heme proteins. This suggests a general strategy employed by Hp and AHSP whereby the FeIII oxidation state is thermodynamically frozen and thus short circuits the subsequent radical generating steps.

Protection provided by haptoglobin (Hp) and alpha hemoglobin stabilizing protein (AHSP) toward cell free hemoglobin and α-hemoglobin subunit: A common strategy to insulate heme induced toxicity

244th National Meeting (2012)

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