TY - JOUR TI - Specific structural elements of the T-box riboswitch drive the two-step binding of the tRNA ligand AU - Zhang, Jiacheng AU - Chetnani, Bhaskar AU - Cormack, Eric D AU - Alonso, Dulce AU - Liu, Wei AU - Mondragón, Alfonso AU - Fei, Jingyi VL - 7 PY - 2018 DA - 2018/09/25 SP - e39518 C1 - eLife 2018;7:e39518 DO - 10.7554/eLife.39518 UR - https://doi.org/10.7554/eLife.39518 AB - T-box riboswitches are cis-regulatory RNA elements that regulate the expression of proteins involved in amino acid biosynthesis and transport by binding to specific tRNAs and sensing their aminoacylation state. While the T-box modular structural elements that recognize different parts of a tRNA have been identified, the kinetic trajectory describing how these interactions are established temporally remains unclear. Using smFRET, we demonstrate that tRNA binds to the riboswitch in two steps, first anticodon recognition followed by the sensing of the 3’ NCCA end, with the second step accompanied by a T-box riboswitch conformational change. Studies on site-specific mutants highlight that specific T-box structural elements drive the two-step binding process in a modular fashion. Our results set up a kinetic framework describing tRNA binding by T-box riboswitches, and suggest such binding mechanism is kinetically beneficial for efficient, co-transcriptional recognition of the cognate tRNA ligand. KW - riboswitch KW - T-box KW - smFRET KW - gene regulation JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -