Question

Describe the two-state allosteric model for O2 binding to hemoglobin (Hb).

Answer 1

Nearly all oxygen in animals is transported by haemoglobin(Hb) and Hb binds with 4 oxygen molecules one after the other.Binding of one oxygen molecule with a haem group facilitate binding of other oxygen molecule with another haem group on same protein and this binding behaviour is called cooperativity

Two state allosteric model for oxygen binding to Hb includes:

• T state:is the tensed state,has less affinity for oxygen and is favoured by tissues
• R state:is the relaxed state,has high affinity for oxygen and is favoured by lungs

T state is dominant conformation of deoxy Hb and stabilized by ionic interactions whereas oxygen binding stabilizes R state

The binding of oxygen to a Hb subunit in the T state triggers change in the conformation to the R state