Multiplicity of different stable quaternary conformations in ferric hemoglobin from Camelus dromedarius. Modulation by small anions.

The effect of small anions in modulating polyphosphate-induced conformational changes in ferric dromedary hemoglobin (Camelus dromedarius) was investigated. The results obtained indicate that: i) in solution, the simultaneous presence of polyphosphate and small anions is essential to obtain quaternary changes in the protein; ii) the charge, rather than the size or sterical configuration, mainly affects the quaternary structural equilibrium of the macromolecule; iii) three distinct, stable quaternary conformers of ferric dromedary hemoglobin were detected spectroscopically as a function of charge and concentration of small anion.