Natural and synthetic polyamines: modulators of signalling proteins

Ionotropic receptors are modulated allosterically by natural polyamines, such as spermine, and by polyamine derivatives, such as polyamine amides (e.g. philanthotoxin-343) and polymethylene tetraamines (e.g. methoctramine. Modulation can be either positive (potentiation) or negative (non-competitive antagonism of either open or closed channel receptor conformation). Photoaffinity labelling studies have identified a site close to the channel lumen on the nicotinic acetylcholine receptor Torpedo electroplax that is probably the allosteric site responsible for antagonism of the closed channel conformation of this receptor. (C) 2000 Elsevier Science S.A. All rights reserved.