Stoddard B L, Cohen B E, Brubaker M, Mesecar A D, Koshland D E
Division of Basic Sciences, Program in Structural Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
Nat Struct Biol. 1998 Oct;5(10):891-7. doi: 10.1038/2331.
The structure of a rate-limited product complex formed during a single initial round of turnover by isocitrate dehydrogenase has been determined. Photolytic liberation of either caged substrate or caged cofactor and Laue X-ray data collection were used to visualize the complex, which has a minimum half-life of approximately 10 milliseconds. The experiment was conducted with three different photoreactive compounds, each possessing a unique mechanism leading to the formation of the enzyme-substrate (ES) complex. Photoreaction efficiency and subsequent substrate affinities and binding rates in the crystal are critical parameters for these experiments. The structure suggests that CO2 dissociation is a rapid event that may help drive product formation, and that small conformational changes may contribute to slow product release.
