Neisserial Opa Protein Dynamics and Interaction with Host Ceacam Receptors

Abstract

Cytochrome c (cyt c) displays a striking ability to perform many seemingly disparate functions within the cell. It is responsible for shuttling electrons between protein complexes in the mitochondria to generate ATP and is also a primary signal for apoptosis when improperly localized as a result of an interaction with the mitochondrial lipid cardiolipin (CL). We utilized reverse micelle nuclear magnetic resonance (RM-NMR) in order to investigate these different functional roles of cyt c at atomic resolution. The chemical shifts of RM encapsulated cyt c are essentially identical to the free solution protein, confirming structural fidelity. We have determined the structure of encapsulated cyt c to high resolution (0.45 Å backbone RMSD, 0.92 Å heavy atom RMSD) using standard solution NMR methods. Using pseudo-contact shifts (PCS), we find that the majority of the protein structure does not change significantly upon change in redox state. A subset of residues localized at the heme-exposed face of the protein undergo small structural changes upon change in redox state, localized to the binding site on cyt c for its BC1 complex partner. The interaction of cyt c with CL was investigated by titration of the lipid into the RM encapsulated protein. The confined space effect upon protein encapsulation in the RM allowed for separation and characterization of this peripheral interaction from the subsequent lipid insertion and unfolding of cyt c. These experiments provide the first detailed interface of the initial, largely electrostatic phase of the interaction. 461-Pos Board B241 Prion Proteins and Mechanisms of Interaction with Model Membranes