engleski

Structural Nonequivalence of the alpha- and beta-Heme-Pockets in Human Methemoglobin. A Proton Magnetic Relaxation Study in Solution

Solvent-proton longitudinal magnetic relaxation rates as dependent on temperature were measured for human (H)/canine (C) valency hybrids of the type {; ; alpha H(III)beta C(II)2}; ; and {; ; alpha C(II)beta H(III)}; ; 2. The two metheme irons in the human methemoglobin chains induce quite different proton magnetic relaxation (pmr) rates reflecting a tighter beta-heme-pocket compared to the alpha subunits. Both heme pockets appears to be loosened in the presence of inositol hexaphosphate (IHP) although this allosteric effector binds only to the beta chains, the binding assumed to be the same for canine as for human hemoglobin. The subunit nonequivalence is retained also in the T-quaternary state induced by IHP. In the species hybrids the pmr rates due to the metheme iron are sensitive to the valency (ligand) state, which was either CO or H2O in the partner half of the hybrid. All results show very clearly the interrelationship of the tertiary (protomer) structure with the quaternary (oligomer) structure in hemoglobin.

Haemoglobin ; Human/canine valency hibrid ; Inositol hexaphosphate ; Proton magnetic relaxation

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