Capture and Release of tRNA by the T-Loop Receptor in the Function of the T-Box Riboswitch

Fang, XianyangMichnicka, MalgorzataZhang, YikanWang, Yun-XingNikonowicz, Edward P.2017-11-142017-11-142017Fang, Xianyang, Michnicka, Malgorzata, Zhang, Yikan, et al.. "Capture and Release of tRNA by the T-Loop Receptor in the Function of the T-Box Riboswitch." <i>Biochemistry,</i> 56, no. 28 (2017) American Chemical Society: 3549-3558. https://doi.org/10.1021/acs.biochem.7b00284.https://hdl.handle.net/1911/98807In Gram-positive bacteria, the tRNA-dependent T-box riboswitch system regulates expression of amino acid biosynthetic and aminoacyl-tRNA synthetase genes through a transcription attenuation mechanism. Binding of uncharged tRNA “closes” the switch, allowing transcription read-through. Structural studies of the 100-nucleotide stem I domain reveal tRNA utilizes base pairing and stacking interactions to bind the stem, but little is known structurally about the 180-nucleotide riboswitch core (stem I, stem III, and antiterminator stem) in complex with tRNA or the mechanism of coupling of the intermolecular binding domains crucial to T-box function. Here we utilize solution structural and biophysical methods to characterize the interplay of the different riboswitch–tRNA contact points using Bacillus subtilis and Oceanobacillus iheyensis glycyl T-box and T-box:tRNA constructs. The data reveal that tRNA:riboswitch core binding at equilibrium involves only Specifier–anticodon and antiterminator–acceptor stem pairing. The elbow:platform stacking interaction observed in studies of the T-box stem I domain is released after pairing between the acceptor stem and the bulge in the antiterminator helix. The results are consistent with the model of T-box riboswitch:tRNA function in which tRNA is captured by stem I of the nascent mRNA followed by stabilization of the antiterminator helix and the paused transcription complex.engThis is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Chemical Society.Capture and Release of tRNA by the T-Loop Receptor in the Function of the T-Box RiboswitchJournal articleTbox_SAXS_BCHM_wFIGShttps://doi.org/10.1021/acs.biochem.7b00284