Myoglobin structure

The protein that I've chosen to look at is myoglobin, which incidentally was the first protein structure to be found. Here is a picture of the structure:


Myoglobin binds carries oxygen in muscles, and binds oxygen at the heme group. The heme group is a porphyrin, which contains an iron atom at the centre. Porphyrins are aromatic molecules which are highly conjugated, usually deeply coloured and like to form complexes with other atoms. In this case, it is iron. The heme group is the red group of atoms at around the middle of the structure. Oxygen molecules bind directly to the iron atom.

The heme group is stabilised by hydrophobic interaction between the pyrrole rings in the porphyrin and hydrophobic amino acids in the interior of the protein. Additionally, a nitrogen atom from a histidine residue above the plane of the heme ring is coordinated with the iron atom, which also stabilises the interaction. I was able to find this particular histidine atom, and while it is still hard to see, it is one of the light green residues with the pentagon-like shape at the end of it in this picture, situated above the plane of the heme ring:

In order to better see the heme group and the binding site, I also made a ribbon structure. The iron atom in the centre of the heme group can easily be seen.