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Binding of a Myristoylated Protein to the Lipid Membrane Influenced by Interactions with the Polar Head Group Region
journal contribution
posted on 2018-10-25, 00:00 authored by Izabella Brand, Dorota Matyszewska, Karl-Wilhelm KochMany
cytoplasmic proteins contain a hydrophobic acyl chain, which
facilitates protein binding to cell membranes. Hydrophobic interactions
between the exposed acyl chain of the protein and hydrocarbon chains
of lipids in the cell membrane are the driving force for this specific
lipid–protein interaction. Recent studies point out that in
addition to hydrophobic interactions the charge–charge and
charge–dipole interactions between the polar head groups and
basic amino acids contribute significantly to the binding process.
Recoverin possesses a myristoyl chain at the N-terminus. In the presence
of Ca2+ ions, the protein undergoes structural rearrangements,
leading to the extrusion of the myristoyl chain, facilitating the
protein binding to the membrane. In this work, we investigate the
impact of interactions between the polar head group region of lipid
molecules and recoverin which binds to the model membrane. The interaction
with a planar lipid bilayer composed of phosphatidylcholine and cholesterol
with myristoylated and nonmyristoylated recoverin is studied by in
situ polarization modulation infrared reflection absorption spectroscopy.
The binding of recoverin to the lipid bilayer depends on the transmembrane
potential, indicating that the orientation of the permanent surface
dipole in the supramolecular assembly of the lipid membrane influences
the protein attachment to the membrane surface. Analysis of the amide
I′ mode indicates that the orientation of recoverin bound to
the lipid bilayer is independent of the presence of myristoyl chain
in the protein and of the folding of the protein into the tense or
relaxed state. In contrast, it changes as a function of the membrane
potential. At positive transmembrane potentials, the α-helical
fragments of recoverin are oriented predominantly parallel to the
bilayer surface. This orientation facilitates the insertion of the
acyl chain of the protein into the hydrophobic region of the bilayer.
At negative transmembrane potentials, the α-helical fragments
of recoverin change their orientation with respect to the membrane
surface, which is followed by the removal of the myristoyl chain from
the membrane.