Erythritol predicted to inhibit permeation of water and solutes through the conducting pore of P. falciparum aquaporin.

Plasmodium falciparum aquaporin (PfAQP) is a multifunctional channel protein in the plasma membrane of the malarial parasite that causes the most severe form of malaria infecting more than a million people a year. This channel protein facilitates transport of water and several solutes across the cell membrane. In order to better elucidate the fundamental interactions between PfAQP and its permeants and among the permeants, I conducted over three microseconds in silico experiments of atomistic models of the PfAQP-membrane system to obtain the free-energy profiles of five permeants (erythritol, water, glycerol, urea, and ammonia) throughout the amphipathic conducting pore of PfAQP. The profiles are analyzed in light of and shown to be consistent with the existent in vitro data. The binding affinities are computed using the free-energy profiles and the permeant fluctuations inside the channel. On this basis, it is predicted that erythritol, a permeant of PfAQP itself having a deep ditch in its permeation passageway, inhibits PfAQP's functions of transporting water and other solutes with an IC50 in the range of high nanomolars. This leads to the possibility that erythritol, a sweetener generally considered safe, may inhibit or kill the malarial parasite in vivo without causing undesired side effects. Experimental studies are hereby called for to directly test this theoretical prediction of erythritol strongly inhibiting PfAQP in vitro and possibly inhibiting P. falciparum in vivo.