Redox Thermodynamics of Cytochromes C Subjected to Urea Induced Unfolding

The thermodynamics of the electron transfer (ET) process for beef heart and yeast cytochromes c and the Lys72Ala/Lys73Ala/Lys79Ala mutant of the latter species subjected to progressive urea-induced unfolding was determined electrochemically. The results indicate the presence of at least three protein forms which were assigned to a low-temperature and a high-temperature His- Met intermediate species and a bis-histidinate form (although the presence of a His-Lys form cannot be excluded