Oxymyoglobin

Oxymyoglobin is a globular protein whose structure is similar to [[myoglobin]]. The major structural difference is that molecular oxygen is bound to the heme in oxymyoglobin whereas it is not in myoglobin. This article will gave an overview of the structural similarities with myoblobin as well as a more detailed description of the structural differences.

=== Structural Similarities ===

Oxymyoglobin is shown with layers of <font color=red>water</font> bound to its surface. This water is strongly attracted to the protein and is part of the structure of any crystalline protein. Hiding the <scene name='Oxymyoglobin/Water_removed/1'>water</scene> reveals that the overall tertiary shape is much like a hockey puck. The <scene name='Oxymyoglobin/Secondary_structure/1'>α-helix</scene> is a prominent secondary structural component. The [[Myoglobin]] page gives more detail on the secondary structure. The а-helices can be shown to form <scene name='Oxymyoglobin/Two_layers/2'>two layers of backbone</scene>, and myoglobin can be classified as an antiparallel α-helix type of globular protein. The <scene name='Oxymyoglobin/Rama/1'>Ramachandran plot</scene> shows most of the residues involved in an α-helix are clustered in the area of the plot where one would expect them to be. (Review [[Ramachandran Plot]].) Many of the residues that are outside of the expected cluster are at the end of a helix, and it is not unusual for such residues to have ψ and φ values that are outside of the range for the α-helix. Also notice that many of the residues that are in the quadrants on the right are Gly. (Residues can be identified by hovering over the sphere with the cursor.) The [[prosthetic group]] of myoglobin is a <scene name='Oxymyoglobin/Heme/2'>heme</scene>, and as shown here it is inserted into a pocket which is nonpolar. Review [[Porphyrin|heme]] structure. <scene name='Oxymyoglobin/His_93/3'>His 93</scene> is attached to one side of the heme.

=== Structural Differences ===

molecular oxygen is attached to the other side