Loss of a primordial identity element for a mammalian mitochondrial aminoacylation system.

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Fender A, Sauter C, Messmer M, Putz J, Giege R, Florentz C, Sissler M

Loss of a primordial identity element for a mammalian mitochondrial aminoacylation system.

J Biol Chem. 2006 Jun 9;281(23):15980-6. Epub 2006 Apr 5.

PubMed ID

16597625 [ View in PubMed

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Abstract

In mammalian mitochondria the translational machinery is of dual origin with tRNAs encoded by a simplified and rapidly evolving mitochondrial (mt) genome and aminoacyl-tRNA synthetases (aaRS) coded by the nuclear genome, and imported. Mt-tRNAs are atypical with biased sequences, size variations in loops and stems, and absence of residues forming classical tertiary interactions, whereas synthetases appear typical. This raises questions about identity elements in mt-tRNAs and adaptation of their cognate mt-aaRSs. We have explored here the human mt-aspartate system in which a prokaryotic-type AspRS, highly similar to the Escherichia coli enzyme, recognizes a bizarre tRNA(Asp). Analysis of human mt-tRNA(Asp) transcripts confirms the identity role of the GUC anticodon as in other aspartylation systems but reveals the non-involvement of position 73. This position is otherwise known as the site of a universally conserved major aspartate identity element, G73, also known as a primordial identity signal. In mt-tRNA(Asp), position 73 can be occupied by any of the four nucleotides without affecting aspartylation. Sequence alignments of various AspRSs allowed placing Gly-269 at a position occupied by Asp-220, the residue contacting G73 in the crystallographic structure of E. coli AspRS-tRNA(Asp) complex. Replacing this glycine by an aspartate renders human mt-AspRS more discriminative to G73. Restriction in the aspartylation identity set, driven by a rapid mutagenic rate of the mt-genome, suggests a reverse evolution of the mt-tRNA(Asp) identity elements in regard to its bacterial ancestor.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Aspartic acid	Aspartate--tRNA ligase, cytoplasmic	Protein	Humans	Unknown	Not Available	Details
Aspartic acid	Aspartate--tRNA ligase, mitochondrial	Protein	Humans	Unknown	Not Available	Details