Formation of Protein Channels in Target Membranes
Many membrane-damaging proteins act at a physical level by inserting themselves into the target lipid bilayer and generating hydrophilic transmembrane channels. The first clear documentation of this principle was made in the complement field, where it was found that self-association of the terminal five serum complement components into channel-forming C5b-9 protein complexes inserting into the target bilayer constituted the molecular principle underlying the phenomenon of immune cytolysis. Subsequently, the recognition emerged that membrane damage by channel formers occurred in a similar fashion in many other instances. The present discussion will focus on the cytolytic C5b-9 complement complex and on two prototypes of channel-forming bacterial exotoxins that we have been studying. Attention will be drawn to the numerous analogies now recognized to exist among these protein systems.
KeywordsProtein Channel Membrane Attack Complex Target Membrane Human Complement Planar Lipid Bilayer
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