Alice Ting was stymied by GFP's many deficiencies ? its large size, poor optical properties, and most importantly, its restriction to optical imaging. So the MIT assistant chemistry professor decided to roll her own labeling technology instead.
The objective, she says, is to migrate from the test tube to the live cell?to study proteins in their natural habitat. It took two years of "high drama," but Ting found a way to combine GFP's genetic flexibility with the nonintrusive elegance of small-molecule probes.
Now she can selectively, and covalently, couple almost any molecular label ? from Alexa fluors to MRI contrast agents ? to specific proteins exclusively on the cell surface.1 "Already we can do things GFP would never have let us do," she says, from monitoring synaptic receptor dimerization, to watching the trafficking of single receptor molecules.
In seeking a high-throughput way to chart the mammalian transforming growth factor-beta ( TGF-beta) signaling network, Jeffrey Wrana of Mount Sinai Hospital, Toronto, was similarly stymied. Coimmunoprecipitation-mass spectrometry identifies the components of a complex, but not their binary connections. As for the yeast two-hybrid assay, says postdoc Miriam Barrios-Rodiles, "The main problem we wanted to address was that interactions in mammalian cells are dynamic. Many of these are dependent on post-translational modifications, which may not occur in yeast."
Barrios-Rodiles spent four years perfecting her workaround, called LUMIER (luminescence- based mammalian interactome mapping).2 Like Y2H, LUMIER relies on pairs of hybrid molecules; like coimmunoprecipitation, it employs affinity pull-down. But where Y2H forces protein fragments into yeast nuclei to activate transcription, LUMIER probes intact proteins in mammalian cells. There's no Western blotting or mass spec step either; detection is via a simple luciferase assay.
Barrios-Rodiles knew she was on to something when, the team identified a novel interaction between TGF-beta and Par6 in a pilot screen. "This could be pretty cool," she thought. "Now we have to find out what it does."
Biochemist Peter Schultz of the Scripps Research Institute, San Diego, had a more fundamental problem. Constrained in his molecular tinkering by 20 natural amino acids, Schultz asked, "Can you develop an approach to expanding the genetic code, given that nature hasn't done it in three billion years?"
Focusing on translational suppression-based approaches, Schultz started with cell-free systems. But to boost production he had to move in vivo. "It's proven successful and surprisingly general," he says; at least 30 novel amino acids have been incorporated into proteins using this approach, in both bacteria and eukaryotes.3 Even Schultz's 16-year-old daughter, Kate, has gotten the system to work. "She's good," he laughs. "But this shows it's a pretty robust technology."
Schultz founded San Diego-based Ambrx to commercialize his procedure's pharmaceutical applications, and according to chief business officer Troy Wilson, the company anticipates commercialization of research tools by mid-2007. My money's on a panel of modified in vitro translation kits, or even reagents supplied as IVT additives; high-yield bacterial strains are also likely.
MIT is negotiating with several biotech firms to market Ting's technology, too. As for Wrana, he hasn't vigorously pursued commercialization. But basic LUMIER should be easy to market: it's just some cloning vectors, luciferase reagents, and protocols. According to Konrad Powell- Jones, a licensing consultant in Mount Sinai's tech transfer office, work to identify licensing partners is imminent. High-throughput LUMIER is a different story, however: Powell-Jones says Mount Sinai has a testing service for academic and industrial clients already up and email@example.com