Miniaturized armless tRNAs – function, interaction, modifications

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In order to function as universal adapters in translation, tRNAs must have structural similarities to be recognized by central components of protein biosynthesis such as translation factors and ribosomes. They therefore have a highly conserved cloverleaf-like secondary structure that folds into a three-dimensional L-shape. Interestingly, tRNAs with significant structural deviations exist in the mitochondria of metazoa, with individual arms of the cloverleaf shape being reduced or missing. We were able to detect the most reduced tRNA forms in the nematode Romanomermis culicivorax, which have only short unpaired connector regions instead of D and T arm elements, resembling a hairpin that folds into a boomerang-like 3D shape. We want to investigate the function of these connector elements with regard to the tRNA structure and the interaction of these extremely reduced tRNAs with the unique mitochondrial elongation factor mt-EF-Tu and thereby determine the evolution of the connectors and the adaptation of the elongation factor. Furthermore, we want to identify specific modifications in the armless tRNAs and investigate their contribution to the formation of a functional tRNA structure. These studies will provide fundamental insights into the surprising flexibility of the mitochondrial translation system, its evolution and the adaptation of protein factors involved.