Title
Conformational properties of cardiolipin-bound cytochrome c
Author
Jonas Hanske, Jason R. Toffey, Anna M. Morenz, Amber J. Bonilla, Katherine H. Schiavoni, Ekaterina V. Pletneva
Year
2012
Journal
PNAS
Abstract
Interactions of cytochrome c (cyt c) with cardiolipin (CL) are important for both electron transfer and apoptotic functions of this protein. A sluggish peroxidase in its native state, when bound to CL, cyt c catalyzes CL peroxidation, which contributes to the protein apoptotic release. The heterogeneous CL-bound cyt c ensemble is difficult to characterize with traditional structural methods and ensemble-averaged probes. We have employed time-resolved FRET measurements to evaluate structural properties of the CL-bound protein in four dansyl (Dns)-labeled variants of horse heart cyt c. The Dns decay curves and extracted Dns-to-heme distance distributions PðrÞ reveal a conformational diversity of the CL-bound cyt c ensemble with distinct populations of the polypeptide structures that vary in their degree of protein unfolding. A fraction of the ensemble is substantially unfolded, with Dns-to-heme distances resembling those in the guanidine hydrochloride-denatured state. These largely open cyt c structures likely dominate the peroxidase activity of the CL-bound cyt c ensemble. Site variations in PðrÞ distributions uncover structural features of the CL-bound cyt c, rationalize previous findings, and implicate the prime role of electrostatic interactions, particularly with the protein C terminus, in the CL-induced unfolding.
Full Article
Instrument
J-715
Keywords
Circular dichroism, Secondary structure, Vesicle interactions, Biochemistry