INTERRELATION BETWEEN THE FUNCTION OF HEME-PROTEINS AND THE STRUCTURAL MODIFICATIONS OF THEIR PROTEIN PARTS

X. ON THE REACTION OF REDUCED HEMOGLOBIN WITH ETHYLISOCYANIDE AND THE EFFECT OF UREA ON THIS REACTION

Abstract

1. Sigmoid coefficient in the reaction of reduced hemoglobin with EIC was calculated to be 2.4 from Hill's equation. This result indicates the existence of heme-heme interaction in the reaction of reduced hemoglobin with EIC.
2. Dissociation constants of heme-linked acid groups of EIC-hemoglobin were assumed to be similar to those of oxyhemoglobin.
3. In the presence of 6.0 M urea, the heme-heme interaction decreased (n decreased from 2.4 to 1.4), EIC-combining affinity increased and the Bohr effect disappeared.
In the presence of urea in lower concentrations, the heme-heme in-teraction did not decrease and the EIC-combining affiinity increased slightly.
4. The Bohr effect disappeared continuously with the increase of urea concentration.
Some discussions were made on the mechanism of the Bohr effect.
The authors are indebted to Prof. K. Kaziro for his continuous help and stimulating discussions. The authors also express their gratitude to the Ministry of Education for assistance from the Scientific Research Fund.