Function and Structure of Hemoglobin and Myoglobin

Myoglobin consists of a single polypeptide chain consisting of 153 amino acids and a size of 18 kDa. Its three-dimensional structure was first determined by X-ray crystallography by John Kendrew in 1957. Myoglobin is a typical globular protein because it is a highly folded and compact structure in which most of the hydrophobic amino acid residues are embedded inside and many polar residues are embedded in the surface. X-ray crystallography shows that a single polypeptide chain of myoglobin consists entirely of eight (labeled A - H) alpha - helices.

In 1959, scientists at the University of Cambridge in the UK have identified the conformation of the two proteins found in almost all multicellular animals, hemoglobin and myoglobin. Hemoglobin is a protein that carries oxygen in the blood. Myoglobin absorbs oxygen from hemoglobin and preserves it in the tissue until it is needed. These are the first three dimensional protein structures that were resolved, and they produced some important insights. Myoglobin has a single strand of 153 amino acids surrounded by a group of iron and other atoms (called "heme") to which oxygen binds. In contrast, hemoglobin consists of four chains: two identical chains of 141 amino acids and two identical chains of 146 amino acids. However, each chain has exactly the same heme as myoglobin, and each of the four chains in the hemoglobin molecule is fully folded with myoglobin. In 1959, the relationship between the two molecules was very closely related.

Iron: About 70% of human iron is contained in blood erythrocytes called hemoglobin and muscle cells called myoglobin. Hemoglobin is essential for transferring oxygen from the lungs to the tissues from the blood. Myoglobin in myocytes receives, stores, transports and releases oxygen. Excessive iron content of the organs necessary for life support can be used to treat liver disease (cirrhosis of the liver, cancer), heart attack or heart failure, diabetes, osteoarthritis, osteoporosis, metabolic syndrome, hypothyroidism even in the case of mild iron overload , Hypogonadism, the risk of multiple symptoms. In some cases, premature death

Like hemoglobin, myoglobin is also a respiratory pigment, but unlike its equivalent, it is in skeletal muscle. Like the hemoglobin molecule subunit, myoglobin has a higher affinity for oxygen than hemoglobin and hence absorbs oxygen from hemoglobin. Only when PO 2 in the skeletal muscle is below 20 mm Hg, it starts to release a large amount of oxygen and acts as an "emergency reserve" for oxygen. However, during normal or moderate activity, myoglobin retains its oxygen and myoglobin abandons its oxygen only during extreme activity where the oxygen partial pressure in the muscle cell becomes zero, and excess oxygen Provide storage.