Thermodynamics of alligator metmyoglobin unfolding.
The conformational free energy of alligator metmyoglobin was examined over a pH range of 4.4-8.0, a temperature range of 18-48 degrees C, and a guanidinium chloride concentration of 0-2.3 M. For isothermal unfolding at 25 degrees C essentially the same value was obtained for the conformational free energy from all the data: 7.0 +/- 0.5 kcal/mol. The cooperativity of the unfolding with respect to denaturant is considerably less than for mammalian myoglobins. On unfolding three to four side chains with a pKa of 6.3 in the unfolded protein are protonated instead of the six expected. The temperature at which delta H (unfolding) is zero is much lower than for previously characterized myoglobins. Alligator metmyoglobin, considerably less stable than other previously characterized myoglobins, may not be as compactly folded.
D000489:Alligators and Crocodiles; D000818:Animals; D006420:Hemeproteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008786:Metmyoglobin / Q000302:isolation & purification / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D011487:Protein Conformation; D011489:Protein Denaturation; D013816:Thermodynamics
D006420:Hemeproteins; D008786:Metmyoglobin