Effect of polyanions on the spectroscopic properties of the nitric oxide derivative of ferrous dromedary (camelus dromedarius) hemoglobin

The effect of inositol hexakisphosphate, 2,3-diphosphoglycerate, dextran sulphate, and heparin on the spectroscopie (absorbance, circular dichroism, EPR) properties of the nitric oxide derivative of ferrous dromedary (Camelus dromedarius) hemoglobin was investigated. The results obtained show that: (i) all polyanions bind to the protein at the same sites, but with different affinities; (ii) polyanions affect the protein conformation of the ferrous nitrosyl derivative in a different way with respect to aquo-ferric and ferrous oxy dromedary hemoglobin; and (iii) the data obtained provide further independent evidence for the existence in dromedary hemoglobin of two functionally distinct polyanion binding sites that affect the conformational equilibrium of the protein in opposite ways.