Characterization of cytochrome c folding intermediates induced by sucrose and phosphate.

Spectroscopic and calorimetric investigations of the folding of denatured cytochrome c in the presence of phosphate ion and sugar were carried out to understand subtle differences in the nature of induced conformation and folding energy landscape. Altered conformations of cyt c induced by sucrose and phosphate, with same absorbance wavelength maxima, exhibit lack of tertiary interactions in segment 70-85 and similar α-helical content. However, compactness, the exposure of the heme to solvent and the secondary structure content in the two conformations are different. Although downhill folding was observed for both conformations, extent of cooperativity is higher in case of phosphate-induced conformation.