Loss of allosteric behaviour in recombinant hemoglobin α 2 β 29r)F8)His→Ala: Restoration upon addition of strong effectors

FEBS Letters

Dumoulin, A.¹  Poyart, C.¹  Kiger, L.¹  Vasseur, C.¹  Marden, M.C.¹  Baudin, V.¹  Sligar, S.G.²  Pagnier, J.¹  Jiang, R.¹ 

[1] Institut National de la Santé et de la Recherche Médicale U 299, Hôpital de Bicêtre, 94275 Le Kremlin-Bicêtre, France;Beckman Institute, 405 N. Mathews Avenue, Urbana, IL 61801, USA

关键词: Recombinant hemoglobin;    Homotropic effect;    Heterotropic effect;    Proximal histidine;    Heme-heme interaction;    Hb;    hemoglobin;    IHP;    inositol hexakisphosphate;    L345;    2-[4-(3;    4;    5-dichlorophenylureido)phenoxy]-2-methylpropionic acid;    PP;    protoporphyrin;   

DOI  :  10.1016/0014-5793(95)01069-Q

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

In the stereochemical model proposed by Perutz [1], the Fe-His(F8) bond plays a significant role in the allosteric transition in hemoglobin and the resulting cooperativity in ligand binding. When this bond is ruptured, there is a loss in the transmission of the information concerning ligand binding; examples are Hb(NO)₄ in the presence of inositol hexakisphosphate (IHP), or nickel substituted Hb hybrids which, despite being liganded, exhibit deoxy-like properties. To study the effects of the loss of the iron proximal histidine bond, we have engineered the α ₂ β ₂(F8)H92A recombinant Hb. The replacement of the highly conserved proximal histidine F8 residue by an alanine results in a low affinity for the heme group and a loss of the allosteric properties; kinetics of CO recombination after photodissociation show only the rapid bimolecular phase, characteristic of the high affinity R-state. However, a significant amount of deoxy (T-state) kinetics are observed after addition of external effectors such as IHP. The iron-histidine bond is apparently crucial for the heme-heme interaction, but the allosteric equilibrium may still be influenced by external constraints.

【 授权许可】

Unknown