Fig. 5. The membrane-bound structure of NHE1-LID.

a QCM-D, with sensor frequency shift (ΔF) on the left y-axis (top lines) and the dissipation factor (ΔD) on the right y-axis (lower lines), colors represent different sensor harmonics reporting on the adsorption of molecules (i.e., lipids and subsequently NHE1-LID) on the sensor surface. Area I to V correspond to the supported lipid bilayer in contact with the sensor (I), injection of MQ water prior (II), injection of the protein solution and its incubation with the membrane (III), removal of excess protein with MQ water (IV) and re-introduction of the buffer (V). b Reflectivity vs. q measured in buffers of different degree of deuteration (see C). c Scattering length density (SLD) profiles obtained from the NR experiment; the experimental data were collected for the sample in contact with buffer prepared with different D₂O content (d-buffer = 100% D₂O, smw-buffer = 38% D₂O:62% H₂O, h-buffer = 100% H₂O). d Per-residue histogram of protein-lipid contacts observed during the MD simulation (blue-gray: POPC, green: POPS). e Temporal evolution of protein-POPC and protein-POPS contacts from the MD simulation. f Snapshots from the MD simulation trajectory depicting the different bound orientations of NHE1-LID on the membrane. NHE1-LID shown in ribbon representation, lipids shown in van der Waals’ representation (hydrogens omitted for clarity), colors as in (D) (H1, blue; H2, red; POPC blue-gray; POPS, green). g Schematic representation of the NR experiment setup. Details on the right side depict the protein-layer thickness measured from NR compared to average thickness of the protein obtained from MD.