Understanding the interactions between anionic
lipid membranes and
amyloidogenic proteins/
peptides is key to elucidate the molecular mechanisms underlying the membrane-driven
amyloid fiber formation. Here, hen egg-white
lysozyme was used as a model
protein to test whether this same process also occurs with non-amyloidogenic
lipid-
binding proteins/
peptides. A complementary set of biophysical techniques was employed to study the structure and dynamics of the
lipid-
lysozyme mixed fibers produced at a low
lipid/
protein molar ratio that have been proposed earlier to present "
amyloid-like" characteristics. The multilamellar architecture of these elongated mesoscopic structures was established by performing time-resolved Förster resonance energy transfer measurements, at both bulk (ensemble) and single-fiber level. The predominantly oligomeric
lysozyme and
phospholipids were both found to display significantly decreased lateral mobility when embedded in these mixed fibers. Notably, two-photon microscopy of
Laurdan revealed that a pronounced membrane surface
dehydration/increased molecular interfacial packing was produced exclusively in these elongated mixed supramolecular fibers present in the highly polymorphic samples. Infrared spectroscopic studies of
lysozyme in these samples further showed that this
protein did not exhibit a rich β-sheet structure characteristic of
amyloid fibrils. These results support the conclusion that negatively charged
lipid membranes do not have the general ability to trigger
amyloid fibril formation of non-
amyloidogenic proteins.