New Sequential Model for Human Hemoglobin: Alpha Subunit as Cooperativity Inducer

Document Type : Article


1 Department of Biology, Faculy of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran

2 Department of Parasitology and Medical Entomology, Tarbiat Modares University, Tehran, Iran

3 Department of Biology, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran


Hemoglobin is a tetrameric oxygen transport protein in animal bodies. However, there is a paucity of information regarding differences between alpha and beta subunits of hemoglobin in terms of oxygen affinity. The sequential model of Koshland, Nemthy and Filmer (KNF model) has attributed similar affinities to both alpha and beta subunits. The main purpose of the present study is to construct a new sequential model for hemoglobin oxygenation based on higher oxygen affinities for alpha subunits. To this end, coordinate files of 19 oxy and 41 deoxy hemoglobin structures were used as starting structures. These files were processed using Microsoft Excel and SPSS software in order to calculate Euclidean distances between each pair of proximal and distal histidine Fe2+ as well as other pairs of atoms of interest. The calculated distances were then compared for either set of hemoglobin conformations, i.e. oxy and deoxy conformations. Our results showed that α2 subunit show higher structural changes that could be related to oxygen affinity. This subunit could be introduced as initiator of hemoglobin oxygenation and cooperativity. Subunit α2 in our sequential model induces relaxed conformation in α1, β2 and β1 respectively. The order of oxygen affinity in our model is as follow: α2 > α1 > β1 > β2.

Graphical Abstract

New Sequential Model for Human Hemoglobin: Alpha Subunit as Cooperativity Inducer


Main Subjects

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