10.1021/acs.langmuir.8b02265.s001 Izabella Brand Izabella Brand Dorota Matyszewska Dorota Matyszewska Karl-Wilhelm Koch Karl-Wilhelm Koch Binding of a Myristoylated Protein to the Lipid Membrane Influenced by Interactions with the Polar Head Group Region American Chemical Society 2018 recoverin Recent studies point lipid bilayer acyl chain transmembrane potentials protein binding head group region α- helical fragments interaction membrane surface Polar Head Group Region myristoyl chain Lipid Membrane Influenced reflection absorption spectroscopy orientation lipid membrane influences 2018-10-25 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Binding_of_a_Myristoylated_Protein_to_the_Lipid_Membrane_Influenced_by_Interactions_with_the_Polar_Head_Group_Region/7315541 Many 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 Ca<sup>2+</sup> 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.