Thermodynamics of carp metmyoglobin unfolding.

The conformational free energy of carp lateral muscle metmyoglobin at 25 degrees C pH 8 is 9.0 +/- 0.5 kcal/mol as estimated from isothermal unfolding by both urea and guanidinium chloride. A novel procedure for the simultaneous analysis of acid and guanidinium chloride unfolding data is described. Acid denaturation data suggest that binding of five protons to histidyl residues occurs on unfolding. Correlation of sequences and conformational stabilities of several myoglobins according to the tertiary structure of sperm whale myoglobin suggests an evolutionary turnover of side chain-side chain interactions.