Poster abstracts

Poster number 55 submitted by Shinichiro Shoji

Effects of antibiotics on spontaneous reverse translocation

Shinichiro Shoji (Department of Microbiology, The Ohio State University), Maria A. Borovinskaya (Physical Biosciences Division, Lawrence Berkeley National Laboratory), Jamie H. Daudna Cate (Physical Biosciences Division, Lawrence Berkeley National Laboratory), Kurt Fredrick (Department of Microbiology, Ohio State Biochemistry Program, The Ohio State University)

Abstract:
A number of antibiotics are known to inhibit EF-G-dependent translocation by interacting with the ribosome. Inhibition may be due to the ability of the antibiotic to stabilize the pretranslocation (PRE) complex, destabilize the transition state of translocation, or confer both of these abilities. We have measured the effect of several translocation inhibitors on spontaneous reverse translocation to help distinguish which potential mechanism is responsible for inhibiting EF-G-dependent (forward) translocation. Tetracycline, spectinomycin, and hygromycin B inhibit spontaneous reverse translocation, suggesting that these antibiotics destabilize the transition state of tRNA-mRNA movement. Streptomycin, aminoglycosides of the neomycin group (neomycin, paromomycin, gentamicin), and viomycin do not inhibit spontaneous reverse translocation. Interestingly, hygromycin B and the latter antibiotics cause conversion of ribosomes from the POST to PRE state in the presence of EF-G and GTP, corroborating earlier evidence that they stabilize the PRE state. On the basis of the newly solved structures of the ribosome complexed with antibiotics, we propose the molecular mechanisms of inhibition of translocation by these antibiotics.

Keywords: ribosome, antibiotics, reverse translocation