Fig. 4. The de-wetting of the pores of TMEM175 and BEST1. (A) The simulation of water molecules (red and white) in the transmembrane pore (blue) of TMEM175. The rings of hydrophobic sidechains lining the pore constriction are shown as pale blue bonds. Water molecules are present in the initial state of the pore (left), which subsequently de-wets (right) within the first few nanoseconds of the simulation. (B) The comparable simulation of water molecules in the transmembrane pore of BEST1. (C) The time course of the de-wetting of the BEST1 pore. The positions of water molecules along the pore axis for the hydrophobic constriction of the BEST1 pore are shown (blue circles), which are taken from the first 10 ns of a MD simulation of the BEST1 channel. It can be seen that there are initially ca. 7 water molecules within the constriction (blue arrows). The pore rapidly de-wets, although occasional sporadic forays of isolated water molecules into the constriction occur, e.g. as indicated by the red arrow.