A macromolecular transducer as illustrated by trout hemoglobin IV

Oxygen binding by trout Hb IV has been investigated as a function of pH up to 10 atmospheres (1 MPa) of pure O2. The results bring out an extreme proton-oxygen linkage, which gives rise to a Root effect. They are discussed in relation to the function of the hemoglobin as an oxygen pump. The system is of special interest as providing a prototype of a macromolecule acting as a transducer by coupling two allosterically linked reactions.