The chloride effect in the human embryonic haemoglobins.
The interactions of the three human embryonic haemoglobins with chloride ions have been investigated. Each of the three embryonic haemoglobins exhibits a unique pattern of oxygen-affinity-dependence on chloride ion concentration. Human embryonic haemoglobin Portland (zeta 2 gamma 2) is found to be completely insensitive to chloride ion concentration. Haemoglobin Gower I (zeta 2 gamma 2) shows a small concentration dependence, whilst haemoglobin Gower II (alpha 2 epsilon 2) exhibits a dependence approaching that of the adult protein. The degree of co-operativity for each protein is essentially chloride concentration independent. The chloride-dependent and -independent components of the alkaline Bohr effects have been measured for each of the embryonic haemoglobins and compared with that of the adult protein. Both the chloride-binding data and the Bohr effect have been analysed in terms of the recently developed allosteric model proposed by Perutz [Perutz, Fermi, Poyart, Pagnier and Kister (1993) J. Mol. Biol. 233, 536-545].
Hofmann
O
O
Biochemistry and Molecular Biology Research Group, School of Biological Sciences, University of Auckland, New Zealand.
Carrucan
G
G
Robson
N
N
Brittain
T
T
D002712:Chlorides / Q000737:chemistry*; D004622:Embryo, Mammalian / Q000737:chemistry; D005319:Fetal Hemoglobin / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000737:chemistry
D002712:Chlorides; D005319:Fetal Hemoglobin; D010100:Oxygen