Crystal Structure of Camel (Camelus dromedarius) Methemoglobin: A High Oxygen Affinity Lowland Species

Hemoglobin (Hb) is an important oxygen carrying protein inherent in erythrocytes facilitates exchange of oxygen and carbon dioxide from body tissues. Bioengineered synthetic erythrocytes with enhanced Hb proteins have been developed as efficient blood transfusion substitutes to supply oxygen to patients in extreme situations. This has driven research towards the molecular characterization and structural elucidation of Hb in organisms thriving in extreme conditions. Camel is recognized as a typical organism to investigate molecular level adaptations to surpass extreme ecological conditions in the arid zone. The molecular architecture of Hb is linked to the oxygen requirements of an organism to sustain at extreme living conditions. Molecular structure of camel Hb can be determined by X-ray crystallography. In this study, camel Hb is purified and crystallized in the monoclinic space group P2₁ with cell dimensions of a = 52.75 Å, b = 116.78 Å, c = 52.80 Å and β = 120.07 Å. The crystal packing parameters reveal that a whole biological molecule is present in the asymmetric unit with the final R-factor and R_free value 23.1 and 29.5%, respectively. The Quaternary structural analysis of the camel Hb [PDB ID: 3GDJ] suggests its state to be identical to human R-state Hb.