Formation of a molten-globule-like state of cytochrome c induced by high concentrations of glycerol

The effect of glycerol on the structure of cytochrome c was investigated by circular dichroism, absorbance and EPR spectroscopy. The results obtained show that an increasing concentration of the organic solvent (70-99.2%, v/v ) in aqueous polyalcohol mixtures converts native cytochrome c into a new, low spin form through a fully reversible, two-state transition. The glycero l-stabilized form (that we call here the G state) retains native-like amoun ts of alpha-helix structure while rigid tertiary structure and native Fe(II I)-Met(80) axial bond are lost. Analysis of data suggests a molten globule character of the G state; support to this view is afforded by the striking similarities between the spectroscopic (and, thus, structural) properties o f the G state with those of the acidic molten globule of the protein (A sta te). (C) 1999 Societe francaise de biochimie et biologie moleculaire / Edit ions scientifiques et medicales Elsevier SAS.