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      Conformational stability and dynamics of cytochrome c affect its alkaline isomerization.

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          Abstract

          The alkaline isomerization of horse heart ferricytochrome c (cyt c) has been studied by electronic absorption spectroscopy in the presence of the Hofmeister series of anions: chloride, bromide, rhodanide and perchlorate. The anions significantly affect the apparent pK (a) value of the transition in a concentration-dependent manner according to their position in the Hofmeister series. The Soret region of the absorption spectra is not affected by the presence of the salts and shows no significant structural perturbation of the heme crevice. In the presence of perchlorate and rhodanide anions, the cyanide exchange rate between the bulk solvent and the binding site is increased. These results imply higher flexibility of the protein structure in the presence of chaotropic salts. The thermal and isothermal denaturations monitored by differential scanning calorimetry and circular dichroism, respectively, showed a decrease in the conformational stability of cyt c in the presence of the chaotropic salts. A positive correlation between the stability, DeltaG, of cyt c and the apparent pK (a) values that characterize the alkaline transition indicates the presence of a thermodynamic linkage between these conformational transitions. In addition, the rate constant of the cyanide binding and the partial molar entropies of anions negatively correlate with the pK (a) values. This indicates the important role of anion-induced solvent reorganization on the structural flexibility of cyt c in the alkaline transitions.

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          Author and article information

          Journal
          J Biol Inorg Chem
          Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry
          Springer Science and Business Media LLC
          0949-8257
          0949-8257
          Feb 2007
          : 12
          : 2
          Affiliations
          [1 ] Department of Biochemistry, Faculty of Science, UPJS, Moyzesova 11, 040 01, Kosice, Slovakia.
          Article
          10.1007/s00775-006-0183-9
          17120073
          97491e87-f68d-4569-958a-4f81f85bed4b
          History

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