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Blood, 15 February 2001, Vol. 97, No. 4, pp. 1099-1105
RED CELLS
Expression, purification, and characterization of human
hemoglobins Gower-1 ( 2 2), Gower-2
( 22), and Portland-2
(2 2) assembled in complex
transgenic-knockout mice
Zhenning He and
J. Eric Russell
From the Departments of Medicine and Pediatrics,
University of Pennsylvania School of Medicine and The Children's
Hospital of Philadelphia, Philadelphia, PA.
Embryonic  - and  -globin subunits assemble with each other and
with adult  - and  -globin subunits into hemoglobin heterotetramers in both primitive and definitive erythrocytes. The properties of these
hemoglobins Hbs Gower-1 (22), Gower-2
(22), and Portland-2 (22)have been incompletely described as
they are difficult to obtain in quantity from either primary human
tissue or conventional expression systems. The generation of complex
transgenic-knockout mice that express these hemoglobins at levels
between 24% and 70% is described, as are efficient methods for their
purification from mouse hemolysates. Key physiological
characteristicsincluding P50, Hill coefficient, Bohr
effect, and affinity for 2,3-BPGwere established for each of the 3 human hemoglobins. The stability of each hemoglobin in the face of
mechanical, thermal, and chemical stresses was also determined.
Analyses indicate that the -for- exchange distinguishing Hb
Portland-2 and Hb A alters hemoglobin O2-transport capacity
by increasing its P50 and decreasing its Bohr effect. By
comparison, the -for- exchange distinguishing Hb Gower-2 and Hb A
has little impact on these same functional parameters. Hb Gower-1,
assembled entirely from embryonic subunits, displays an elevated
P50 level, a reduced Bohr effect, and increased 2,3-BPG
binding compared to Hb A. The data support the hypothesis that Hb
Gower-2, assembled from reactivated globin in individuals with
defined hemoglobinopathies and thalassemias, would serve as a
physiologically acceptable substitute for deficient or dysfunctional Hb
A. In addition, the unexpected properties of Hb Gower-1 call into
question a common hypothesis for its primary role in embryonic development.
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