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.)