Magnesium-dependent alternative foldings of active and inactive Escherichia coli tRNAGIU revealed by chemical probing

• Published in: Nucleic acids research Vol. 27; no. 17; pp. 3583 - 3588
• Main Authors: Madore, Eric, Florentz, Catherine, Giegé, Richard, Lapointe, Jacques
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.09.1999
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/27.17.3583

A stable conformer of Escherichia coli tRNAGlu, obtained in the absence of Mg2+, is inactive in the aminoacylation reaction. Probing it with diethylpyro-carbonate, dimethyl sulfate and ribonuclease V1 revealed that it has a hairpin structure with two internal loops; the helical segments at both extremities have the same structure as the acceptor stem and the anticodon arm of the native conformer of tRNAGlu and the middle helix is formed of nucleotides from the D-loop (G15–C20:2) and parts of the T-loop and stem (G51–C56), with G19 bulging out. This model is consistent with other known properties of this inactive conformer, including its capacity to dimerize. Therefore, this tRNA requires magnesium to acquire a conformation that can be aminoacylated, as others require a post-transcriptional modification to reach this active conformation.