Fluorescent Probe Detects Terrorism Toxin Activity

By inserting a fluorescent probe into an RNA strand, researchers at the University of California, San Diego, have developed an assay method to detect potential terrorism agents such as ricin and saporin (Angew. Chem. Int. Ed. 2008, 47, 6661). Known as ribosome-inactivating proteins (RIPs), ricin and saporin remove the purine base from a specific nucleotide residue in a conserved sequence of ribosomal RNA. Once the base is removed, the ribosome loses affinity for proteins known as elongation factors that facilitate protein synthesis. Current approaches for detecting RIPs involve time-consuming immunoassays using radiolabeled antibodies. Yitzhak Tor and colleagues at UCSD have now developed a simpler and faster approach by incorporating a thienopyrimidine-based fluorescent probe into an RNA sequence complementary to the conserved ribosomal loop, with the probe located in the position opposite the depurination site. When the probe is free in solution, it fluoresces; when it binds to an intact ribosome sequence, the fluorescence is quenched; and when it binds to a depurinated ribosome loop, the fluorescence reappears. The technique could allow real-time detection of ricin and saporin activity, the authors say, and could be useful in identifying RIP inhibitors.