Myoglobin is a protein found in the muscle tissue of most mammals. It has a significant job in the body and is extremely important. This was also the first protein that had its 3D structure revealed by X-Ray Crystallography in 1958.
The structure of myoglobin consists of eight alpha helices that are connected by loops. It also contains a porphyrin ring with an iron at its center, and consists of 153 amino acids.
Myoglobin, unlike hemoglobin, only has one globulin group and has a higher affinity for oxygen. Iron within the heme group must be in the Fe+2 state to bind oxygen. If iron is oxidized to the Fe+3 state, metmyoglobin is formed which has a completely different structure, functi9on and mechanism.
Myoglobin is found in the muscles of animals, and it is an oxygen-storing unit, known to provide oxygen to muscles that are working. It also has a number of enzymatic functions, such as the decomposition of bioactive nitric oxide to nitrate. It is an oxygen-binding protein, and works to temporarily provide oxygen when the blood oxygen is insufficient. The more myoglobin that is found in the muscles, the longer a mammal is going to be able to hold their breath at any given time.
The distal imidazole is not bonded to the iron but is available to interact with the substrate O2. This interaction encourages the binding of O2, but not carbon monoxide (CO), which still binds about 240× more strongly than O2.