The effect of evolution on the structure of tuna myoglobin

The circular dichroic activity of tuna myoglobin in the far ultraviolet has been found to be lower than that of mammalian myoglobin, thus indicating a lower content of alpha-helix. Fluorescence and absorption studies have indicated that the structure of the N-terminal region of the molecule is essentially the same in all the examined apomyoglobins, whereas differences have been observed in the heme microenvironment. The prediction of secondary structure has revealed that the alpha-helical segments of tuna myoglobin, especially those involved in the formation of the heme pocket, are shorter than those of sperm whale myoglobin.