ISSN:
1573-4943
Keywords:
Hemoglobin
;
tetramer strength
;
delta gene
;
allosteric regulator
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Hemoglobin A2 (α2δ2), which is present at low concentration (1–2%) in the circulating red cells of normal individuals, has two important features that merit its study, i.e., it inhibits polymerization of sickle HbS and its elevated concentration in some thalassemias is a useful clinical diagnostic. However, reports on its functional properties regarding O2 binding are conflicting. We have attempted to resolve these discrepancies by expressing, for the first time, recombinant hemoglobin A2 and systematically studying its functional properties. The construct expressing HbA2 contains only α and δ genes so that the extensive purification required to isolate natural HbA2 is circumvented. Although natural hemoglobin A2 is expressed at low levels in vivo, the amount of recombinant α2δ2 expressed in yeast is similar to that found for adult hemoglobin A and for fetal hemoglobin F when the α + β or the α + γ genes, respectively, are present on the construct. Recombinant HbA2 is stable, i.e., not easily oxidized, and it is a cooperative functional hemoglobin with tetramer-dimer dissociation properties like those of adult HbA. However, its intrinsic oxygen affinity and response to the allosteric regulators chloride and 2,3-diphosphoglycerate are lower than the corresponding properties for adult hemoglobin. Molecular modeling studies which attempt to understand these properties of HbA2 are described.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1007196118200
