Myoglobin is a protein that binds iron and oxygen that is present in the muscle tissues of the vertebrates in all mammals. It is associated with hemoglobin, which is the protein that binds the iron and the oxygen in the blood, especially in the red blood cells. Myoglobin is found in the bloodstream only after muscle injury in humans. Myoglobin is also known as the dominant pigment of tissue muscles that carry oxygen. Muscle cells containing high levels of myoglobin grant organisms the ability to hold their breath for a longer time. Mammals like seals and whales have abundant myoglobin in their blood cells allowing them to hold their breath. Myoglobin is said to be absent in smooth muscles, however it is said to be present in in Type I muscle, Type II A and Type II B.
The first three-dimensional structure that was acknowledged by X-ray crystallography was that of the myoglobin protein. John Kendrew reported this accomplishment in the year of 1958 along with his associates and bagged the Nobel Prize in Chemistry along with Max Perutz. Though the study of myoglobin in biology is said to be the most studied protein, the physiological activity of this protein is not decisively determined. Myoglobin is put into code by the MB gene in humans.
Hemoglobin has the ability to form into methemoglobin, oxyhemoglobin and carboxyhemoglobin; likewise myoglobin has the ability to take the form of metmyoglobin, carboxymyoglobin and oxymyoglobin. Myoglobin is a cytoplasmic protein by which the oxygen is bound on a heme group which is similar to hemoglobin. However, hemoglobin has four groups and myoglobin can only port one group, but also has higher inclination towards oxygen than hemoglobin does. This diversity is associated with the different roles played by both; hemoglobin is used to transport oxygen and myoglobin is used to store the oxygen. Myoglobin is emitted by tissues of the muscle that are damaged, which have high levels of the protein. The myoglobin that is emitted by these tissues is then refined by the kidneys, however it is said to be harmful to the renal tubular epithelium and can cause severe kidney injury.High levels of myoglobin found in blood can cause to change the color of the urine to dark red-brown. Myoglobin is also said to be the O2 storage protein in muscles, possessing the ability to emit O22 at the time of anoxia and hypoxia. The procedure of monitoring the levels of myoglobin in the blood or urine has been utilized in order to detect cardiac muscle or skeletal injuries in the human body.