Direct observation of two distinct affinity conformations in the T state human deoxyhemoglobin

FEBS Letters

Shibayama, Naoya¹  Saigo, Satoshi¹ 

[1] Department of Physics, Jichi Medical School, Yakushiji 3311-1, Minamikawachi, Kawachi, Tochigi 329-0498, Japan

关键词: Hemoglobin;    Allostery;    Cooperative effect;    Monod–Wyman–Changeux model;    Sol-gel;    MWC;    Monod–Wyman–Changeux;    IHP;    inositol hexaphosphate;    HEPES;    N-[2-hydroxyethyl]piperazine-N′-(2-ethanesulfonic acid);   

DOI  :  10.1016/S0014-5793(01)02225-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The main features of cooperative oxygenation of human hemoglobin have been described by assuming the equilibrium between two affinity conformations of the entire molecule, T and R. However, the molecular basis for explaining the wide variation in the O₂ affinities of the deoxy T state has remained obscure. We address this long-standing issue by trapping the conformational states of deoxyhemoglobin molecules within wet porous transparent silicate sol-gels. The equilibrium O₂ binding measurements of the encapsulated deoxyhemoglobin samples showed that deoxyhemoglobin free of anions coexists in two conformations that differ in O₂ affinity by 40 times or more, and addition of inositol hexaphosphate to this anion-free deoxyhemoglobin brings about a very slow redistribution of these affinity conformations. These results are the first, direct demonstration of the existence of equilibrium between two (at least two) functionally distinguishable conformational states in the T state deoxyhemoglobin.

【 授权许可】

Unknown