title: Losing the stem-loop structure from metazoan mitochondrial tRNAs and co-evolution of interacting factors.
abstract: Conventional tRNAs have highly conserved sequences, four-armed cloverleaf secondary structures, and L-shaped tertiary structures. However, metazoan mitochondrial tRNAs contain several exceptional structures. Almost all tRNAs(Ser) for AGY/N codons lack the D-arm. Furthermore, in some nematodes, no four-armed cloverleaf-type tRNAs are present: two tRNAs(Ser) without the D-arm and 20 tRNAs without the T-arm are found. Previously, we showed that in nematode mitochondria, an extra elongation factor Tu (EF-Tu) has evolved to support interaction with tRNAs lacking the T-arm, which interact with C-terminal domain 3 in conventional EF-Tu. Recent mitochondrial genome analyses have suggested that in metazoan lineages other than nematodes, tRNAs without the T-arm are present. Furthermore, even more simplified tRNAs are predicted in some lineages. In this review, we discuss mitochondrial tRNAs with divergent structures, as well as protein factors, including EF-Tu, that support the function of truncated metazoan mitochondrial tRNAs.
authors.affiliation: Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo Tokyo, Japan.
authors.forename: Yoh-Ichi
authors.initials: Y
authors.lastname: Watanabe
authors.affiliation: Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo Tokyo, Japan.
authors.forename: Takuma
authors.initials: T
authors.lastname: Suematsu
authors.affiliation: Department of Biotechnology, Okayama University Okayama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohtsuki
keywords: D-arm; T-arm; aminoacyl-tRNA synthetase; elongation factor Tu; mitochondrial tRNA; ribosome; tRNA nucleotidyltransferase