HOMOLOGY MODELING OF RING NECKED PHEASANT (PHASIANUS COLCHICUS, GALLIFORMES) MAJOR HEMOGLOBIN COMPONENT (HBA)

Abstract

Birds have a specialized system of respiration. Their hemoglobin has been adapted to a vast variety of environmental conditions. To understand their specialized mechanism of respiration we need to understand the three dimensional (3D) structure of its hemoglobin. In this study, we have built a three dimensional homology model of hemoglobin A (HbA) from Phasianus colchicus using the 3D structure coordinates of Meleagris gallopavo (common turkey) HbA as template. The model was built with the help of MODELLER 9v8 and was evaluated with ProSA and PROCHECK. The present study is about the analysis of effects of intersubunit contacts on oxygen affinity of the hemoglobin. The effect of the following pairs of intersubunit contacts on the oxygen affinity of the hemoglobin have been studied i.e. αA99 with β101, αA34 with β125, αA38 with β99 and β97, and β55 with αA119. Due to the larger distances between these pairs of residues hydrogen bond is absent between them as has been predicted by the homology model. It has been predicted that the absence of hydrogen bonds between the above mentioned residues might have increased the oxygen affinity of the HbA of P. colchicus except the first pair of residues (αA99 with β101) which has been suggested to have lowered the oxygen affinity of the hemoglobin. This study also involves the analysis of the evolutionary relationship of Galliformes with thirteen selected orders of Aves.