Partial sequence of hemoglobin from cobra (Naja naja naja)

Functional properties of the hemoglobin from the South American snake Mastigodryas bifossatus

The hemolysate of Mastigodryas bifossatus shows two major hemoglobins with very close isoelectric points, and four different globin chains. The stripped hemolysate exhibits a low alkaline Bohr effect (delta log P50/delta pH = -0.30 between pH 7 and 8) and a decrease of the co-operativity from 2.3 to unity when the pH increases from 6.15 to 8.5. In the presence of ATP, large changes in the oxygen affinity and co-operativity are observed. The Bohr effect rises to -0.46 and the n50 values stay at around 3 in the pH range 6-9. An increase in temperature induces a large decrease in the oxygen affinity for the stripped hemolysate. In the pH range between 7.5 and 8.5, the values of delta H in kcal/M are around 10 fold larger for the stripped protein than for the protein in the presence of ATP. Measurements of rapid kinetics of oxygen dissociation and carbon monoxide binding reflect the ATP sensitivity observed in equilibrium experiments.