Modification of the wobble uridine (U₃₄) in mitochondrial and bacterial tRNAs.

<p>Schema of the U₃₄ modification pathways in human and yeast mt-tRNAs and <i>Escherichia coli</i> tRNAs <b>(A)</b> and <i>A</i>. <i>suum</i> mt-tRNAs <b>(B)</b>. In A, proteins GTPBP3, MTO1, and TRMU (also named MTU1) from humans, and MSS1, MTO1, and MTU1, from yeast, are orthologous of the bacterial MnmE, MnmG and MnmA proteins, respectively. Taurine (humans) and glycine (<i>E</i>. <i>coli</i> and yeast) are used to introduce the τm and cmnm groups into position 5 of U₃₄. In B, MTCU-1, MTCU-2 and MTTU-1 are the nematode orthologues of GTPBP3, MTO1, and TRMU, respectively, and their roles are inferred from studies of the <i>E</i>. <i>coli</i> and yeast proteins. The fractions of <i>A</i>. <i>suum</i> modified mt-tRNAs, according to the study by Sakurai <i>et al</i>. [<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1006921#pgen.1006921.ref028" target="_blank">28</a>], are indicated below the schema. Note that mt-tRNA^Glu, mt-tRNA^Lys and mt-tRNA^Gln are fully modified at position 5 but lack thiolation at position 2, whereas most (~90%) is modified at both positions (2 and 5), and about 50% of mt-tRNA^Trp molecules do not contain any modification at the U₃₄.