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Hemoglobine is the protein that transports oxygen in the blood. It is an allosteric protein that changes shape when it binds to oxygen. Hemoglobin is the protein that makes blood red. In mammals, this protein makes up about 97% of the red blood cells dry content, and around 35% of the total content including water.Hemoglobine in the blood carries oxygen from the respiratory organs to the rest of the body where it releases the oxygen to burn the nutrients to provide energy to power the functions of the organism and collects the resultant carbon dioxide to bring it back to the respiratory organs which would be dispensed from the organism. Hemoglobine picks up the largest possible load of oxygen in the lungs and delivers all of it where and when needed. The molecule also carries the important regulatory molecule nitric oxide which is bound to the globin protein thiol group and it is released at the same time with oxygen. Nitric oxide affects the walls of blood vessels and helps in their relaxation. Hemoglobine also helps in the regulation of blood pressure by distributing nitric acid through blood.

sickle cell hemoglobine

Hemoglobin deficiency can be cause either by decreased amount of hemoglobin molecules, as in anemia, or by decreased ability of each molecule to bind oxygen. In both cases, hemoglobin deficiency decreases blood oxygen carrying capacity. Other factors that cause the low hemoglobin are: the loss of blood, nutritional deficiency, chemotherapy, kidney failure, or abnormal hemoglobin.
High hemoglobin levels can be caused by exposure to high altitudes, smoking, dehydration, or tumor.
The decrease of hemoglobin leads to the symptoms of anemia.
 The genes for the protein chains of hemoglobin show small differences within different human populations, so the amino acid sequence is slightly different from person to person. In most cases the changes do not affect protein functions. However, in some cases these different amino acids lead to major structural changes. On such example is that of the sickle cell hemoglobin, where glutamate 6 in the beta chain is mutated to valine. This change allows the dexygenated form of the hemoglobin to stick to each other so they produce stiff fibers of hemoglobine inside red blood cells. This in turn deforms the red blood cell, which normally has a smoth disk shape. The mutations in the globin chain have led to diseases such as sickle cell disease and thalassemia.

Ref work





http://www.pdb.org/pdb/101/motm.do?momID=41
David,G; Dutta,S; Molecule of the month (May, 2003) doi:10.2210