Conformation-dependent participation of the protein in electron equivalent transfer to cytochrome c.

When ferricytochrome c is reduced by H atoms (produced by pulse radiolysis) at neutral pH where it is in a closed protein configuration, a considerable percentage of the reduction proceeds through electron equivalent transfer via the protein. At pH 2.0, where cytochrome c is in an open configuration, H atoms reduce by adding directly to the heme porphyrin. The intermediate then observed is identified through similarity with that formed on ferriheme alone.