Functional Nonequivalence of α and β Hemes in Human Adult Hemoglobin |
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| Authors: | Ted R. Lindstrom and Chien Ho |
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| Affiliation: | .Department of Biophysics and Microbiology, Faculty of Arts and Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15213;.Department of Biochemistry, Faculty of Arts and Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15213 |
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| Abstract: | Nuclear magnetic resonance studies of the contact-shifted spectra of heme protons in deoxyhemoglobin A from human adults show conclusively that oxygen binds to the alpha hemes in preference to the beta hemes. The preferential binding is produced in 10% hemoglobin solution at neutral pH by either a 15-fold molar excess of 2,3-diphosphoglycerate or a 5-fold molar excess of inositol hexaphosphate. Preferential binding is not observable in the absence of the organic phosphates. The results indicate that the oxygenation of hemoglobin may be described by a sequential model, or by a concerted model that allows the alpha hemes to bind ligand first. |
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