Water movement in voltage-gated proton channel (HV1)

ALVEAR-ARIAS, JUAN JOSÉ; FERNÁNDEZ, MIGUEL; PEÑA-PICHICOI, ANTONIO; CARRILLO, CHRISTIAN; BASÁEZ, DARÍO; OZU, MARCELO; GARATE, JOSÉ ANTONIO; GONZÁLEZ, CARLOS

San Diego

Congreso; 67th Annual Meeting of the Biophysical Society; 2023

Biophysical Society

The permeation mechanism of the Hv1 channel to date has been controversial, due the lack of an open structure. There are two models discussed to date which propose different things for the H+ permeation in the protein. One postulate state that permeation occurs in a Grotthuss-like manner on a H2O continuum when the channel is in its conductive configuration. While the other posture states that a water cable crosses the protein, and it is interrupted by the interaction between the selectivity filter (SF) and the 2nd or 3rd arginine of the voltage sensor. Both models do not satisfy experimental evidence as despite the large amount of data suggesting that highly conserved S4 asparagine is important for channel conduction, the current models do not contemplate a role for it in the permeation of the channel. Since the conduction mechanism of H+ cannot be separated from the nature of H2O, by electrophysiological techniques, we evaluate how different mutations directed to N264 CiHv1 channel, affect the H+ conduction properties, and by classical MD simulations we explore how the hydration profiles of the protein, the dipole angle of H2O molecules along the protein and the H2O permeation changes with different N264 mutations. Interestingly, the super-conductive N264E construct have favorable electrostatic profile and the H2O molecules near the SF have more degrees of freedom, while low-conductive N264R have an unfavorable electrostatic profile and a virtually dry zone near to the SF. Additionally, we observed that X. laevis oocytes expressing Hv1 possess an increased osmotic permeability, suggesting H2O fluxes though Hv1 channel. With this study we were able to increase the understanding on the H+ conduction in Hv1 channels and complement the proposed models to expand the variables that govern this process. Thus, in our model we state that the Hv1 conduction possess two main components: (1) the H2O configurations along the protein and (2) the electrostatic profile.