Hemoglobin Dallas (alpha 97(G4)Asn-->Lys): functional characterization of a high oxygen affinity natural mutant.
Hemoglobin Dallas, an alpha-chain variant with a substitution of lysine for asparagine at position 97(G4), was found to have increased oxygen affinity (p1/2 = 1 mmHg at pH 7.3 and 20 degrees C), diminished cooperativity (n, the Hill coefficient = 1.7) and reduced Bohr effect (about 50%). Addition of allosteric effectors (such as 2,3-diphosphoglycerate, inositol hexakisphosphate and bezafibrate) led to a decrease in oxygen affinity and increase in cooperative energy. Kinetic studies at pH 7.0 and 20 degrees C revealed that (i), the overall rate of oxygen dissociation is 1.4-fold slower than that for HbA and (ii), the carbon monoxide dissociation rate is unaffected. The abnormal properties of this hemoglobin variant can be attributed to a more 'relaxed' T-state.
Lendaro
E
E
CNR, Center of Molecular Biology, University La Sapienza, Rome, Italy.
Ippoliti
R
R
Brancaccio
A
A
Bellelli
A
A
Vallone
B
B
Ivaldi
G
G
Sciarratta
G V
GV
Castello
C
C
Tomova
S
S
Brunori
M
M
D000494:Allosteric Regulation; D006455:Hemoglobins, Abnormal / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D010100:Oxygen / Q000378:metabolism*
D006455:Hemoglobins, Abnormal; C077414:hemoglobin Dallas; D010100:Oxygen