Correlation between unfolded states of apocytochrome c and its ability to pass lipid bilayer

In contrast to the horse heart apocytochrome c, the chicken heart apocytochrome c underwent a conformational change from random coil to partial folding during a renaturation process. When the apocytochrome horse heart and that of chicken heart c were subjected to a translocation assay in vitro using large trypsin-enclosed unilamellar vesicles from soybean phospholipids, the ability of the chicken heart apocytochrome c to penetrate into the liposomes was found to decrease markedly with the renaturation procedure, while that of horse heart apocytochrome c remained relatively constant. Observations from circular dichroism measurement on the induction of secondary folding of these two species of apocytochrome c upon interaction with soybean phospholipid vesicles suggested that a more flexible structure of apocytochrome c embedded in the lipid matrix be required for its efficient translocation across the bilayer.