Source: Wikipedia and some random lecture I once had
Myoglobin is a protein that consists of 153 amino acids and a heme (iron containing porphyrim) prosthetic group
Myoglobin is the primary oxygen-carrying pigment of muscle tissues (found in muscles, stores oxygen).
The structure of the myoglobin protein is specifically adapted to provide a pocket to bind the heme group.
Role in Disease:
Myoglobin is released from damaged muscle tissue (rhabdomyolysis), which has very high concentrations of myoglobin. The released myoglobin is filtered by the kidneys but is toxic to the renal tubular epithelium and so may cause acute renal failure.
Myoglobin is a sensitive marker for muscle injury, making it a potential marker for heart attack in patients with chest pain. Its lack of specificity and the cost of the analysis has prevented its widespread use.