A new study in the June issue of Nature Methods expands on a powerful, previously described technique for the targeted deactivation of specific protein kinases. These findings promise to considerably simplify the study of this very important class of proteins.
Protein kinases are actively involved in nearly every important cellular process. There are more than 500 protein kinases encoded in the human genome, and many have yet to be characterized. One of the best ways to do this is by chemically shutting them off, and observing the impact of this deactivation. Unfortunately, many of the currently available drugs lack strong specificity - rather than precisely blocking the action of a single protein kinase, they instead behave like a bull in a china shop, confounding experiments by interfering with the activity of a wide range of unintended targets.
Researchers in the lab of Kevan Shokat discovered one way around this. These drugs show broad specificity because they target a functional domain that is highly conserved throughout the kinase family: the ATP-binding pocket. Shokat found a key amino acid, dubbed the 'gatekeeper', which appears to play a prominent role in determining which molecules can bind the pocket (see Nature 407, 395-401; 2000). A protein kinase with a mutated 'gatekeeper' can be specifically targeted with inhibitors and activators that have no effect on naturally occurring kinases with an intact gatekeeper.
This was a significant breakthrough, but some protein kinases will not accept the gatekeeper mutation. Shokat's group now describes a screen that was conducted to analyze several of these 'unsuitable' protein kinases. Their findings enabled them to develop an effective strategy for the identification of additional mutations that can be introduced to stabilize and maintain the function of gatekeeper-mutant proteins.
This strategy could render many more protein kinases amenable to gatekeeper targeting - good news for researchers studying the hundreds of 'mystery' kinases. Benjamin Cravatt further explores the importance of this study in an accompanying News and Views piece, suggesting that this approach could also assist in developing tools for the study of many other enzyme classes.
Kevan M. Shokat (University of California, San Francisco, CA, USA)
Benjamin F. Cravatt (The Scripps Research Institute, La Jolla, CA, USA)
(C) Nature Methods press release.
Message posted by: Trevor M. D'Souza