Tertiary structure base pairs between D- and TpsiC-loops of Escherichia coli tRNALeu play important roles in both aminoacylation and editing

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Abstract
To ensure the fidelity of protein biosynthesis, aminoacyl‐tRNA synthetases (aaRSs) must recognize the tRNA identity elements of their cognate tRNAs and discriminate their cognate amino acids from structurally similar ones through a proofreading (editing) reaction. For a better understanding of these processes, we investigated the role of tRNALeu tertiary structure in the aminoacylation and editing reactions catalyzed by leucyl‐tRNA synthetase (LeuRS). We constructed a series of Escherichia coli tRNALeu mutated transcripts with alterations of the nucleotides involved in tertiary interactions. Our results revealed that any disturbance of the tertiary interaction between the tRNALeu D‐ and TψC‐loops affected both its aminoacylation ability and its ability to stimulate the editing reaction. Moreover, we found that the various tertiary interactions between the D‐ and TψC‐loops (G18:U55, G19:C56 and U54:A58) functioned differently within the aminoacylation and editing reactions. In these two reactions, the role of base pair 19:56 was closely correlated and dependent on the hydrogen bond number. In contrast, U54:A58 was more important in aminoacylation than in editing. Taken together, our results suggest that the elbow region of tRNA formed by the tertiary interactions between the D‐ and TψC‐loops affects the interactions between tRNA and aaRS effectively both in aminoacylation and in editing.