Conversion of a transmembrane to a watersoluble protein complex by a single point mutation

Abstract

Proteins exist in one of two generally incompatible states: either membrane associated or soluble. Pore-forming proteins are exceptional because they are synthesized as a watersoluble molecule but end up being located in the membrane - that is, they are nonconstitutive membrane proteins. Here we report the pronounced effect of the single point mutation Y221G of the pore-forming toxin aerolysin. This mutation blocks the hemolytic activity of the toxin but does not affect its initial structure, its ability to bind to cell-surface receptors or its capacity to form heptamers, which constitute the channel-forming unit. The overall structure of the Y221G protein as analyzed by cryo-negative staini..