Fluorescence methods to study lipid-protein association: The interaction of protein kinase C with lipid-loaded mixed micelles.

The interaction of protein kinase C with lipids was studied in a mixed micellar system. Two fluorescence spectroscopic methods are presented with a different but complementary information content. Diffusion monitored by fluorescence correlation spectroscopy provides information on the interaction of the protein with the whole lipid aggregate. Resonance energy transfer from tryptophans to pyrene-labeled lipids monitored by time-correlated single-photon counting supplies information on the interaction of the protein with specific lipid cofactors within the micelle. The results can be extended to postulate new mechanisms for the activation of protein kinase C by the signal transduction cascades in the cell. Both fluorescence spectroscopic methods can be easily applied to other protein systems which interact with lipids.