Supplementary Figure 8: Putative model of Hv1 gating.

(a) Putative sequence of molecular motions leading to channel opening. Arrangement of the S1 and S4 segments in the resting state was taken from the mHv1cc crystal structure¹ and modified to obtain putative activated and open states. The S2 and S3 segments have been removed for clarity. The beige shape represents the solvent-inaccessible volume of the S1-S4 region of the mHv1cc chimera generated with a probe radius of 1.4 Å (~ radius of a water molecule). Water-accessible cavities inside the channel are represented in blue. α-carbon positions of key residues are shown as spheres: D1 (pink), S4’s arginines (blue) and the four internal S1 residues with state-dependent accessibility, V151, I153, I154, and V157 (green). Voltage-sensing step: outward motion and rotation of S4 to place R3 in register with D1. Opening step: putative rearrangement of the internal side of S1, which opens a wide intracellular cavity (in blue) up to the selectivity filter residues D1 and R3 and exposes S1 internal residues (green spheres) to the solvent. (b-d) mHv1cc chimera internal vestibule is too narrow to allow access of MTSET to S1 internal residues in the closed state. (b-c) Water-accessible surface of residues from the mHv1cc crystal structure¹ viewed (b) from the side, S1 and S3 in the foreground; and (c) from the entrance of the intracellular vestibule (arrow in (b)). Surface was created with a probe of 1.4 Å radius and color-coded based on residue hydrophobicity, from brown to blue (hydrophobic to hydrophilic). Solvent accessible surfaces of residues equivalent to CiHv1 internal residues whose MTSET accessibility changes during gating, namely I153, I154, and V157 (I101, I102, and V105, respectively, in mHv1cc), are colored in red, green and yellow, respectively. Residues blocking access of internal MTSET to I153 and I154, S1’s H150 (Q98 in mHv1cc), S2’s I206 (I154 in mHv1cc), and S4’s I262 (I208 in mHv1cc) are shown in purple in Corey-Pauling-Koltun (CPK) representation. (d) Close-up view, from the same orientation as in (c), on residues blocking MTSET access to I153 and I154, depicted in purple CPK (CiHv1 numbering in purple, mHv1cc numbering in black). I153 and I154 depicted as red and green sticks, respectively. The three residues define a passage to I153 and I154 of 2.7 Å radius (yellow sphere), smaller than the radius of MTSET, which is approx. 3 Å.

1. Takeshita, K. et al. X-ray crystal structure of voltage-gated proton channel. Nat Struct Mol Biol (2014).