Description of the Function of Myoglobin and the Elucidation of Its 3D Structure
Myoglobin (Mb) is protein that binds and stores oxygen in the muscles.  Under aerobic stress, however, myoglobin releases its bound oxygen to muscle tissue thereby helping mitochodria maintain energy production through oxidative phosphorylation. The image here is that of sperm whale oxymyoglobin consisting of a single polypeptide chain comprised of 153 amino acid residues and a noncovalently-bound heme group composed of a porphyrin ring chelated to an iron (Fe) atom. The iron atom reversibly chelates one oxygen (O2) molecule. Since the polypeptide chain of Mb has no affinity for oxygen itself, the heme group is referred to as a "prosthetic group."  The net mass or MW of Mb is 18 kilodaltons (18 kD). 
The X-ray crystal structure of sperm whale oxyMb at the right as determined by John Kendrew and his colleagues.  Each atom in this structure is positioned by a unique vector relative to the crystal axes.  The atomic position of each atom is stored in the Brookhaven Protein Data Bank (PDB) coordinate file named, 1mbo.pdb.  This file is freely downloadable over the Internet, as are structure files for thousands of other biomolecules. 
(Links to other X-ray coordinate files can be found here.)
© Duane W. Sears
October 07, 2010