Tighter tethering of the CTD to the membrane in K62W channels. (A) Ribbon diagrams, colored to indicate the conformational displacement perpendicular to the membrane plane (along the z axis) between the Apo-K62W and PIP₂-bound WT (3SPI) structures. Positive distances indicate that the corresponding residues in the first structure are closer to the membrane plane. (B) Ribbon diagram showing overlaid structures of Apo-K62W (orange) and PIP₂-bound WT (blue). The residues directly interacting with PIP₂ are shown in sticks and labeled in blue, and residue 62 for bulk anionic lipid binding is shown in sticks and labeled in red. (C) Three independent MD simulations were performed for 100 ns, with PIP₂-bound WT (3SPI) and K62W mutant structures. After 5-ns equilibration, hydrogen bond formation between PIP₂ and neighboring basic residues (Arg78, Arg80, Lys 183, Arg186, Lys188, and Arg189) was assessed, based on the distance (3.5 Å) between donor and acceptor atoms and D-A-H angle (<30^o). The results are means ± SD, three independent simulations of 100 ns in each case and of four tetramers in each case. (D) Snapshots showing details of the PIP₂-binding site in the PIP₂-bound WT (3SPI; left) and K62W (right) structures after 100 ns. Hydrogen bonds between PIP₂ and the neighboring residues (yellow sticks) are shown as black dashes.