The characterization of adult human myoglobin.

It has been reported that crystalline human myoglobin can be resolved by electrophoresis on paper into three components (1,2). Two of these possess nearly identical absorption spectra between 500 and 600 rnp and give the same reactions with oxygen. Although it was suggested that these components differ structurally (2), no evidence has been presented to support this view. In the present study the heterogeneity of human metmyoglobin has been examined with the aid of ion exchange chromatography. Five chromatographically distinct fractions, two of which represent approximately 75% of the myoglobin in skeletal muscle, have been found. Chemical and physical analyses of these fractions indicate that the globin is identical in the two myoglobins that are present in major amount. The differences in chromatographic and electrophoretic behavior of these fractions result from differences in the state of the iron in the heme prosthetic group. At least one of the other myoglobin components, which represents only a minor amount of the myoglobin of normal muscle, appears to differ in the primary structure of the globin moiety. The availability of large amounts of chromatographitally pure myoglobin has prompted further characterization of this protein.