THE CHLORIDE EFFECT IN THE HUMAN EMBRYONIC HEMOGLOBINS

The interactions of the three human embryonic haemoglobins with chlori de ions have been investigated. Each of the three embryonic haemoglobi ns exhibits a unique pattern of oxygen-affinity-dependence on chloride ion concentration. Human embryonic haemoglobin Portland (zeta(2) gamm a(2)) is found to be completely insensitive to chloride ion concentrat ion. Haemoglobin Gower I (zeta(2) gamma(2)) shows a small concentratio n dependence, whilst haemoglobin cower II (alpha(2) epsilon(2)) exhibi ts a dependence approaching that of the adult protein. The degree of c o-operativity for each protein is essentially chloride concentration i ndependent. The chloride-dependent and -independent components of the alkaline Bohr effects have been measured for each of the embryonic hae moglobins and compared with that of the adult protein. Both the chlori de-binding data and the Bohr effect have been analysed in terms of the recently developed allosteric model proposed by Perutz.