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Coupled reactions in hemoglobin. Heme-globin and dimer-dimer association
1Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA.
The Journal of Biological Chemistry
|June 9, 1995
Summary
The study reveals that the separation of hemoglobin (Hb) tetramers into dimers and heme from globin are linked. This finding provides new insights into hemoglobin
Area of Science:
- Biochemistry
- Molecular Biology
- Physiology
Background:
- Hemoglobin (Hb) is crucial for oxygen transport.
- Understanding Hb's dissociation dynamics is key to its function.
- Previous studies explored Hb tetramer-dimer equilibrium.
Purpose of the Study:
- To investigate the linkage between hemoglobin tetramer-dimer dissociation and heme-globin dissociation.
- To determine the heme-globin dissociation rate constants for Hb tetramers and dimers.
- To calculate the tetramer-dimer dissociation constant (K4,2) and compare it with existing data.
Main Methods:
- Utilized spectrophotometric measurements to monitor the initial rate of heme transfer from Hb to serum albumin.
- Conducted experiments across a 3000-fold range of Hb concentrations.
- Employed kinetic analysis to derive dissociation rate constants and the K4,2 value.
Main Results:
- Successfully determined the heme-globin dissociation rate constants for both Hb tetramers and dimers.
- Calculated the tetramer-dimer dissociation constant (K4,2) from kinetic data.
- Observed good agreement between calculated K4,2 values and those obtained by direct methods across five human hemoglobins.
Conclusions:
- Confirmed the postulate that hemoglobin tetramer-dimer dissociation and heme-globin dissociation are linked reactions.
- Provided a novel kinetic method for assessing Hb tetramer-dimer dissociation.
- Discussed the implications of this linkage in relation to classical hemoglobin allosteric properties.