The mitochondrial Leucyl-tRNA synthetase (mtLeuRS) of certain Caenorhabditis species contains an idiosyncratic C-terminal addition. Bioinformatic analyses identified this domain in the mtLeuRS and also four putative nuclear localization sequences (NLSs) encoded within the domain (Ezak, Hong, Chaparro-Garcia, & Ferkey, 2010). This C-terminal extension of Caenrhabditis mitochondrial LeuRS, or CECL domain, is highly positively charged and shows no obvious homologs in protein databases. Bioinformatic and computational modeling suggest that CECL is an added domain rather than being a part of the canonical C-terminal domain. An annotated splice-variant of the mitochondrial LeuRS hints at a mechanism for subcellular localization. Deletion of CECL from the chromosome prevents homozygous worms from surviving fertilization in most cases. From these observations, we hypothesize that the mitochondrial LeuRS of C. elegans performs an alternate nuclear function, perhaps carried out specifically in the neurons of the animal
