Eucaryotic homologues of MnmE and GidA (termed MSS1 and Mto1, respectively, in yeast) are targeted to mitochondria [12],[13], and the human homologues (termed hGTPBP3 and Mto1, respectively) have been implicated in the development of severe mitochondrial myopathies such as MERRF (myoclenic epilepsy ragged red fibres), MELAS (mitochondrial encephalomyopathy lactic acidosis stroke), and nonsyndromic deafness [14]–[18]. Here, MTO1 is linked to mitochondrial encephalomyopathy.