Snake toxins from mamba venoms: unique tools for the physiologist.

Snake venoms are complex mixtures of small molecules, peptides and proteins. Most of the biologically active toxins are peptides or enzymes. The peptides belong to several structural classes, and they have many different biological actions. The best characterised are the so-called three-finger toxins that have three peptide loops stabilised by four disulphide bridges. Despite their common 3D shape, these peptides can interfere selectively with different biological targets, including nicotinic and muscarinic acetylcholine receptors, acetylcholinesterase, ion channels, and cell membranes. Other small peptides can block K+ or Ca2+ channels and are based on Kunitz serine proteinase inhibitors. This article summarises the proteins and peptides isolated from venoms of mamba snakes (Dendroaspis genus) that have been useful as experimental tools for physiologists and pharmacologists.