Structural and functional aspects of the heart ventricle myoglobin of bluefin tuna

The heart ventricle myoglobin of bluefin tuna has been purified to an apparent homogeneity. The amino acid analysis has revealed only a limited number of substitutions between the myoglobins of yellowfin and bluefin tuna. The alpha-helix content of tuna myoglobin has been found considerably lower than that of mammalian myoglobin. No correlation has been discovered between the conformational stability and alpha-helix content. Denaturation experiments have shown that the whole structure of tuna myoglobin results from the interaction of two structural units which represent the product of independent folding processes. The structure of tuna myoglobin has been found more open and disorganized than that of sperm whale. This result has been related to the low content of electrostatic interactions and explained in terms of evolutive adaptations.