Characterization of permeation pathways appearing in the host membrane of Plasmodium falciparum infected red blood cells.

The host cell membrane of Plasmodium falciparum infected cells becomes permeabilized at the trophozoite stage. A variety of otherwise impermeant substances such as carbohydrates, polyols, amino acids and anions easily gain access to the cytosol of infected cells. Using the isotonic-hemolysis method or uptake of labeled substances, we characterized the new permeation pathways as pores of approximately 0.7 nm equivalent radius. The pores bear a positively charged character which facilitates movement of small anions and excludes cations, so that the ionic composition and osmotic properties of infected cells are not drastically altered. Substances of a molecular size similar to that of disaccharides are fully excluded. Substances of limiting size might be accommodated in the pore, provided they bear a side group of hydrophobic character. The new permeation pathways may provide a vital route for acquisition or release of essential nutrients or catabolites.