Oxygen equilibria of human hemoglobin valency hybrids

Oxygen Equilibrium Properties of Chromium(III)-Iron(II) Hybrid Hemoglobins

“…Cyanomet valency hybrid Hbs have been frequently used for studying the oxygenation intermediates of Hb A (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Structural and functional studies on cyanomet valency hybrids have suggested that cyanide-bound ferric heme mimics natural oxyheme, thus deoxy-cyanomet valency hybrid Hbs have been used as models for the intermediate species formed during the cooperative oxygenation process (13)(14)(15)(16)(17)(18)(19)(20).…”

“…Human adult hemoglobin (Hb A) 1 cooperatively binds four oxygen molecules via a complex sequence of intermediate oxygenated states. Information about the intermediate species is required to understand the cooperative mechanism of Hb A, yet little is known about such intermediates because the equilibrium concentrations of the intermediates under any conditions are markedly reduced by the cooperativity of Hb.…”

Nuclear magnetic resonance study of heme-heme interaction in hemoglobin M Milwaukee: implications concerning the mechanism of cooperative ligand binding in normal hemoglobin.

“…In these hemoglobin molecules, the heme groups in either the a-or ,8-chains are selectively oxidized, whereas the other hemes remain in the ferrous state capable of binding 02 or CO (such as a2+/32 or a2/32+). They are generally assumed to be similar in structure to partially oxygen-ligated molecules of normal hemoglobin, such as a2°g#2 or a2(232 (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). The structural and functional properties of the mutant hemoglobins M, which are naturally occurring valency hybrids, have also been studied extensively (15)(16)(17)(18)(19)(20)(21)(22).…”

The Contribution of the Asymmetric α1β1 Half-oxygenated Intermediate to Human Hemoglobin Cooperativity

“…Although cooperative oxygenation of human adult hemoglobin (HbA) 1 has been studied extensively as a paradigm for regulatory actions of allosteric proteins, the functional and structural properties of its eight partially oxygenated intermediates remain elusive. This is mostly due to the strong cooperativity of Hb, which suppresses relative abundance of the intermediates, precluding direct study.…”

“…This is mostly due to the strong cooperativity of Hb, which suppresses relative abundance of the intermediates, precluding direct study. One of the most specific methods for studying the oxygenation intermediates has been to substitute the heme in one or more of four subunits with another metalloprotoporphyrin IX, which does not bind O 2 while mimicking either normal deoxyheme or oxyheme (1)(2)(3)(4)(5)(6). However, there has been a limitation to this approach: Six asymmetric forms cannot be studied in isolation, because the asymmetric hybrid tetramers dissociate into dimers, which then reassociate to form not only the former asymmetric tetramers but also symmetric ones (i.e.…”