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Membrane docking mode of the C2 domain of PKCε: An infrared spectroscopy and FRET study

Abstract:

The C2 domain of PKCε binds to negatively charged phospholipids but little is known so far about the docking orientation of this domain when it is bound. By using a FRET assay we have studied the binding of this domain to model membranes. We have also used ATR-Fourier transform infrared spectroscopy with polarized light (ATR-FTIR) to determine the docking mode by calculating the β-sandwich orientation when the domain is bound to different types of model membranes. The vesicle lipid compositions were: POPC/POPE/POPA (22:36:42) imitating the inner leaflet of a plasma membrane, POPC/POPA (50:50) in which POPE has been eliminated with respect to the former composition and POPC/POPE/CL (43:36:21) imitating the inner mitochondrial membrane. Results show that the β-sandwich of the PKCα-C2 domain is inclined at an angle α close to 45 to the membrane normal. Some differences were found with respect to the extent of binding as a function of phospholipid composition and small changes on secondary structure were only evident when the domain was bound to model membranes of POPC/POPA: in this case, the percentage of β-sheet of the C2 domain increases if compared with the secondary structure of the domain in the absence of vesicles. With respect to the β-sandwich orientation, when the domain is bound to POPC/POPE/CL membranes it forms an angle with the normal to the surface of the lipid bilayer (39) smaller than that one observed when the domain interacts with vesicles of POPC/POPA (49). © 2012 Elsevier B.V. All rights reserved.