The unfolding of the cytochromes c in methanol and acid.

The cytochromes c are a family of hemoproteins that share a number of structural features: a thioether linkage between the protein and the heme, histidine and methionine as the fifth and sixth iron ligands, and a tertiary structure known as the "cytochrome fold." These proteins follow a common mechanism of equilibrium unfolding in methanol and acid, differing only in their reactivity to the denaturing conditions. The reduced cytochromes c exhibit an increased conformational stability which is consistent with the presence of a strengthened iron-methionine linkage in the reduced state.