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Protein Sci 2012 Oct;21(10):1444-55

Familial secondary erythrocytosis due to increased oxygen affinity is caused by destabilization of the T state of hemoglobin brigham (alpha(2) beta(2) (Pro100Leu) ).

Mollan TL, Abraham B, Strader MB, Jia Y, Lozier JN, Olson JS, Alayash AI


Hemoglobin Brigham (ß Pro100 to Leu) was first reported in a patient with familial erythrocytosis. Erythrocytes of an affected individual from the same family contain both HbA and Hb Brigham and exhibit elevated O(2) affinity compared to normal cells (P(50) = 23 mm Hg versus 31 mm Hg at pH 7.4 at 37 (O) C). O(2) affinities measured for hemolysates were sensitive to changes in pH or chloride concentrations, indicating little change in the Bohr and Chloride Effects. Hb Brigham was separated from normal HbA by non-denaturing cation exchange liquid chromatography, and the amino acid substitution was verified by mass spectrometry. The properties of Hb Brigham isolated from the patient's blood were then compared to those of recombinant Hb Brigham expressed in E. coli. Kinetic experiments suggest that the rate constants for ligand binding and release in the high (R) and low (T) affinity quaternary states of Hb Brigham are similar to those of native hemoglobin. However, the Brigham mutation decreases the T to R equilibrium constant (L) which accelerates the switch to the R state during ligand binding to deoxyHb increasing, the rate of association by ~2-fold, and decelerates the switch during ligand dissociation from HbO(2) , decreasing the rate ~2-fold. These kinetic data help explain the high O(2) affinity characteristics of Hb Brigham and provide further evidence for the importance of the contribution of Pro100 to intersubunit contacts and stabilization of the T quaternary structure.

Category: Journal Article
PubMed ID: #22821886 DOI: 10.1002/pro.2130
Includes FDA Authors from Scientific Area(s): Biologics
Entry Created: 2012-07-24 Entry Last Modified: 2012-10-28