Myoglobin

Myoglobin is a protein that is able to bind oxygen. Myoglobin, which is similar to haemoglobin, is the main oxygen-carrying pigment of muscle tissues. Like haemoglobin, it has a porphyrin ring with an iron atom at its centre. It is in the muscle tissue of most mammals. Seals and other marine mammals have more myoglobin in their muscles than land animals. 
In humans, increased level of myoglobin in the serum of the blood can be an indication of myocardial infarction. Other factors for a higher level can be damage to the muscles, epileptic seizures, polytrauma. If the value is much too high, this can lead to kidney failure.
Myoglobin belongs to the globin superfamily of proteins, and as with other globins, consists of eight alpha helices connected by loops. Myoglobin has 153 amino acids.