Temperature perturbation of the allosteric equilibrium in trout hemoglobin.

The carbon monoxide binding kinetics of the isolated trout Hb I has been investigated by flash photolysis at various temperatures, from approximately 20 degrees to 72 degrees C. The time course of recombination has been quantitatively analyzed with a simple two-state allosteric model, making use of the thermodynamic data previously obtained. These new experiments and their analysis show that a simple two-state kinetic model is adequate, in the case of trout Hb I, to describe quantitatively the time course of CO binding at all temperatures. Moreover, we show that temperature can be used to perturb the quaternary conformational equilibrium, the high affinity state of the molecule (R) being progressively more populated at higher temperatures.