Recent developments in structural studies on acetylcholinesterase.

This review focuses on several recent developments concerning structure-function relationships in vertebrate acetylcholinesterase. These include studies on high-resolution structures of human acetylcholinesterase and its complexes; the first crystal structure of a snake venom acetylcholinesterase, in which open and closed states of the 'back door' are visualized; a powerful algorithm for redesigning proteins for enhanced expression in prokaryotic systems, as applied to human acetylcholinesterase, which has hitherto been an intractable target; in situ implementation of 'click chemistry' in crystalline acetylcholinesterase, which yields novel insights into the steric and dynamic changes involved in the reaction within the active-site gorge; and a study that demonstrates the effect of crystallization conditions on ligand alignment within a protein complex, in this case the methylene blue-Torpedo californica acetylcholinesterase complex, which highlights the relevance of the precipitant employed to structure-based drug design. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms.