Static Laue diffraction studies on acetylcholinesterase

Acetylcholinesterase (AChE) is one of nature's fastest enzymes, despite the fact that its three-dimensional structure reveals its active site to be de eply sequestered within the molecule. This raises questions with respect to traffic of substrate to, and products from, the active site, which may be investigated by time-resolved crystallography. In order to address one aspe ct of the feasibility of performing time-resolved studies on AChE, a data s et has been collected using the Laue technique on a trigonal crystal of Tor pedo californica AChE soaked with the reversible inhibitor edrophonium, usi ng a total X-ray exposure time of 24 ms. Electron-density maps obtained fro m the Laue data, which are of surprisingly good quality compared with simil ar maps from monochromatic data, show essentially the same features. They c learly reveal the bound ligand, as well as a structural change in the confo rmation of the active-site Ser200 induced upon binding.