Myoglobin

Myoglobin is a compact globular protein consisting of just 153 amino acids. The single polypeptide is found in muscles and provides vital stores of  oxygen to the muscle cells when required. Myoglobin, like haemoglobin,, binds to oxygen through its iron containing haem group. It is primarily this iron which gives muscle its red colour. The alpha helical 3D structure of the protein was one of the first to be discovered by John Kendrew who studied myoglobin in sperm whales using x-ray crystallography.