Oxygen equilibrium and electron paramagnetic resonance studies on copper(II)‐iron(II) hybrid hemoglobins at room temperature

[摘要]

Copper(II_-iron(II) hybrid hemoglobins, in which hemes in either the α or β subunits are substituted with copper (II) protoporphyrin IX, have been prepared. The affinities of the ferrous-subunits in both hybrids for the first binding oxygen are as low as the affinity of deoxyhemoglobin under various solution conditions, indicating the equality of behavior in copper(II) protoporphyrin IX and deoxyheme. Electron paramagnetic resonance (EPR) examinations on these hybrids at room temperature show that the interaction between copper(II) and the proximal histidine (F8) is specifically weakened in the α subunits within a low affinity conformation of hemoglobin. These results suggest that copper(II) protoporphyrin IX is a useful EPR probe at room temperature for investigating the deoxyheme environment in hemoglobin.

[学科分类] 生物化学/生物物理

[关键词] Hemoglobin;EPR;Metal-substitution;Oxygenation;Intermediate species;Hb;hemoglobin;Hb A;human adult hemoglobin;Mb;myoglobin;EPR;electron paramagnetic resonance;M-Fe hybrid Hb;mixed metal hybrid hemoglobin in which hemes in either the α or β subunits are substituted with metal ion;M;Cu(II)-PPIX;copper(II) protoporphyrin IX;Cu(II)-TPP;copper(II) (meso)-tetraphenylporphyrin;α 2(Cu)β 2(Fe);hybrid hemoglobin containing copper(II) protoporphyrin IX in the α subunits and ferrous protoporphyrin IX in the β subunits;α 2(Fe)β 2(Cu);hybrid hemoglobin complementary with the preceding one;Cu(II)Hb;hemoglobin in which hemes in both the α and β subunits are substituted with copper(II) protoporphyrin IX;Cu(II)Mb;myoglobin in which heme is substituted with copper(II) protoporphyrin IX;EPR;electron paramagnetic resonance;Ni(II)-PPIX;nickel(II) protoporphyrin IX;Ni(II)Hb;hemoglobin in which hemes in both the α and β subunits are substituted with nickel(II) protoporphyrin IX;Bistris;2-[bis(2hydroxyethyl)amino]-2-(hydroxymethyl)-1;3-propanediol;Tris;tris;(hydroxymethyl)aminomethane