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Adaptation of the Romanomermis culicivorax CCA-Adding Enzyme to Miniaturized Armless tRNA Substrates.


ABSTRACT: The mitochondrial genome of the nematode Romanomermis culicivorax encodes for miniaturized hairpin-like tRNA molecules that lack D- as well as T-arms, strongly deviating from the consensus cloverleaf. The single tRNA nucleotidyltransferase of this organism is fully active on armless tRNAs, while the human counterpart is not able to add a complete CCA-end. Transplanting single regions of the Romanomermis enzyme into the human counterpart, we identified a beta-turn element of the catalytic core that-when inserted into the human enzyme-confers full CCA-adding activity on armless tRNAs. This region, originally identified to position the 3'-end of the tRNA primer in the catalytic core, dramatically increases the enzyme's substrate affinity. While conventional tRNA substrates bind to the enzyme by interactions with the T-arm, this is not possible in the case of armless tRNAs, and the strong contribution of the beta-turn compensates for an otherwise too weak interaction required for the addition of a complete CCA-terminus. This compensation demonstrates the remarkable evolutionary plasticity of the catalytic core elements of this enzyme to adapt to unconventional tRNA substrates.

SUBMITTER: Hennig O 

PROVIDER: S-EPMC7730189 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Adaptation of the <i>Romanomermis culicivorax</i> CCA-Adding Enzyme to Miniaturized Armless tRNA Substrates.

Hennig Oliver O   Philipp Susanne S   Bonin Sonja S   Rollet Kévin K   Kolberg Tim T   Jühling Tina T   Betat Heike H   Sauter Claude C   Mörl Mario M  

International journal of molecular sciences 20201128 23


The mitochondrial genome of the nematode <i>Romanomermis culicivorax</i> encodes for miniaturized hairpin-like tRNA molecules that lack D- as well as T-arms, strongly deviating from the consensus cloverleaf. The single tRNA nucleotidyltransferase of this organism is fully active on armless tRNAs, while the human counterpart is not able to add a complete CCA-end. Transplanting single regions of the <i>Romanomermis</i> enzyme into the human counterpart, we identified a beta-turn element of the cat  ...[more]

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