Cytochrome c (cyt c) interactions with cardiolipin (CL) are important for its function in both apoptosis and electron transfer. When bound to CL-containing membranes, cyt c partially unfolds.  ATP is a known binder of folded cyt c, but its effects on the conformational ensemble of CL-bound cyt c are unclear. In this study, we differentiate effects of ionic strength and the phosphonucleotide moiety on the cyt c conformations bound to CL-containing vesicles. Ultracentrifugation assays showed reduced cyt c-lipid binding in the presence of either salt or ATP.  Measurements of resonance energy transfer from a dansyl chromophore to the heme in four site-specifically labeled variants revealed populations of folded and unfolded protein conformations.  Both ATP and salt induce recovery of the folded species, but under the same ionic strength conditions ATP is less effective than salt. These results suggest that ATP may be important in stabilizing lipid-unfolded cyt c conformations.

ATP effects on cardiolipin unfolded cytochrome <i>c</i>

243rd National Meeting (2012)

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ATP effects on cardiolipin unfolded cytochrome c