TY - JOUR TI - Ribosome•RelA structures reveal the mechanism of stringent response activation AU - Loveland, Anna B AU - Bah, Eugene AU - Madireddy, Rohini AU - Zhang, Ying AU - Brilot, Axel F AU - Grigorieff, Nikolaus AU - Korostelev, Andrei A A2 - Green, Rachel VL - 5 PY - 2016 DA - 2016/07/19 SP - e17029 C1 - eLife 2016;5:e17029 DO - 10.7554/eLife.17029 UR - https://doi.org/10.7554/eLife.17029 AB - Stringent response is a conserved bacterial stress response underlying virulence and antibiotic resistance. RelA/SpoT-homolog proteins synthesize transcriptional modulators (p)ppGpp, allowing bacteria to adapt to stress. RelA is activated during amino-acid starvation, when cognate deacyl-tRNA binds to the ribosomal A (aminoacyl-tRNA) site. We report four cryo-EM structures of E. coli RelA bound to the 70S ribosome, in the absence and presence of deacyl-tRNA accommodating in the 30S A site. The boomerang-shaped RelA with a wingspan of more than 100 Å wraps around the A/R (30S A-site/RelA-bound) tRNA. The CCA end of the A/R tRNA pins the central TGS domain against the 30S subunit, presenting the (p)ppGpp-synthetase domain near the 30S spur. The ribosome and A/R tRNA are captured in three conformations, revealing hitherto elusive states of tRNA engagement with the ribosomal decoding center. Decoding-center rearrangements are coupled with the step-wise 30S-subunit 'closure', providing insights into the dynamics of high-fidelity tRNA decoding. KW - RelA KW - ribosome KW - stringent response KW - cryo-EM KW - cognate tRNA KW - decoding JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -