Research Notes

Understanding how bacteria resist antibiotics lies at the crux of staying ahead in the resistance game. A research group at the New York State Health Department's Wadsworth Center in Albany offers a vivid view of how a bacterial protein called Tet (0) shoves aside the antibiotic tetracycline. (C.M.T. Spahn et al., "Localization of the ribosomal protection protein Tet (0) on the ribosome and the mechanisms of tetracycline resistance." Molecular Cell, 7[5]:1037-45, May 2001.) To be an effective drug, an antibiotic must target a part of the protein synthetic machinery that is present in the bacteria cell but not in human cells. The ribosome is one such area of distinction. "Tetracycline normally binds the center of the small subunit of the ribosome and prevents binding of incoming tRNA, interfering in protein synthesis," says Christian Spahn, a postdoctoral associate in the laboratory of Joachim Frank, director of the computational biology and molecular imaging laboratory and a Howard Hughes Medical Institute investigator. Frank pioneered cryo-EM technology, which quickly freezes thousands of Escherichia coli ribosomes caught blocking tetracycline, thus enabling subsequent SPIDER software analysis. Cryo-EM previously revealed that the ribosome has subregions, described as "heads," "shoulders" "stalks" and "platforms," that subtly shift as a protein forms (J. Frank, R.K. Agrawal, "A ratchet-like inter-subunit reorganization of the ribosome during translocation," Nature, 406:318-22, July 20, 2000). Against this backdrop, Spahn showed how Tet (0) slips in at a region called helix 34, where it sufficiently alters the local conformation to destabilize antibiotic binding.