Water movement in CiHv1 channel and its role in proton permeation

ALVEAR-ARIAS, JUAN JOSÉ; FERNÁNDEZ, MIGUEL; BASÁEZ, DARÍO; ORELLANA, FABIÁN; OZU, MARCELO; GARATE, JOSÉ ANTONIO; GONZÁLEZ, CARLOS

Rosario

Congreso; L Reunión Anual de la Sociedad Argentina de Biofísica; 2022

Sociedad Argentina de Biofísica

The permeation mechanism of the Hv1 channel to date has beencontroversial, due the lack of an open structure. There are two modelsdiscussed to date which propose different things for the H+permeation in the protein. One postulate state that permeation occurs in aGrotthuss-like manner on a H2O continuum when the channel is in itsconductive configuration. While the other posture states that a water cablecrosses the protein, and it is interrupted by the interaction between theselectivity filter (SF) and the 2nd or 3rd arginine ofthe voltage sensor. Both models do not satisfy experimental evidence as despitethe large amount of data suggesting that highly conserved S4 asparagine isimportant for channel conduction, the current models do not contemplate a rolefor it in the permeation of the channel. Since the conduction mechanism of H+cannot be separated from the nature of H2O, by electrophysiologicaltechniques, we evaluate how different mutations directed to N264 CiHv1 channel,affect the H+ conduction properties, and by classical MD simulationswe explore how the hydration profiles of the protein, the dipole angle of H2Omolecules along the protein and the H2O permeation changes withdifferent N264 mutations. Interestingly, the super-conductive N264E constructhave favorable electrostatic profile and the H2O molecules near theSF have more degrees of freedom, while low-conductive N264R have an unfavorableelectrostatic profile and a virtually dry zone near to the SF. Additionally, weobserved that X. laevis oocytes expressing Hv1 possess an increasedosmotic permeability, suggesting H2O fluxes though Hv1 channel. Withthis study we were able to increase the understanding on the H+ conduction inHv1 channels and complement the proposed models to expand the variables thatgovern this process. Thus, in our model we state that the Hv1 conduction possesstwo main components: (1) the H2O configurations along the proteinand (2) the electrostatic profile.