What was the game-changing technical breakthrough?
"I'm always asked that question," Stevens said, "and the answer is that there wasn't just one breakthrough, there were about 15 separate developments, each one critically needed in combination with one another, and they came together after a long time. These are the results of 20 years of commitment by several international groups moving the field forward and the critical decision by the NIH Common Fund to focus on membrane protein technology development as a priority area of importance and investment for all of the NIH institutes."
Some of these breakthroughs have improved researchers' ability to produce and purify GPCRs in quantities sufficient for crystallizationa process akin to uranium enrichment. Other breakthroughs have been aimed at stabilizing GPCRs, whose core structure is made up of seven membrane-bound helical elements. "When you take away the membrane, these helices have the potential to fall apart," Stevens said. "It is possible that human GPCRs evolved to be unstable as part of their natural function to avoid over stimulation or signaling."
Over the past eight years, researchers with funding from the NIH Common Fund have developed and improved three key GPCR stabilization and crystallization techniques: the use of fusion proteins that stabilize the basic GPCR structure and make it more crystallizable without affecting its function (Chun et al., Structure, 20, 967, 2012); the use of drug compounds that bind to a GPCR and hold it in a specific functional conformation (Xu et al., Science, 332, 322, 2011); and the use of a membrane-mimicking matrix of fat and water molecules, called the lipidic cubic phase (LCP), in which GPCRs, cholesterol, and ligands can form crystals more readily than they do in traditional detergent solutions.
Improvements in these techniques have come by automating and expanding the LCP tool set. Stevens and Ass
|Contact: Mika Ono|
Scripps Research Institute