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Translocation within the acceptor helix of a major tRNA identity determinant
Author(s) -
Lovato Martha A.,
Chihade Joseph W.,
Schimmel Paul
Publication year - 2001
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/20.17.4846
Subject(s) - biology , library science , chemistry , computer science
The genetic code is defined by the specific aminoacylations of tRNAs by aminoacyl‐tRNA synthetases. Although the synthetases are widely conserved through evolution, aminoacylation of a given tRNA is often system specific—a synthetase from one source will not acylate its cognate tRNA from another. This system specificity is due commonly to variations in the sequence of a critical tRNA identity element. In bacteria and the cytoplasm of eukaryotes, an acceptor stem G3:U70 base pair marks a tRNA for aminoacylation with alanine. In contrast, Drosophila melanogaster (Dm) mitochondrial (mt) tRNA Ala has a G2:U71 but not a G3:U70 pair. Here we show that this translocated G:U and the adjacent G3:C70 are major determinants for recognition by Dm mt alanyl‐tRNA synthetase (AlaRS). Additionally, G:U at the 3:70 position serves as an anti‐determinant for Dm mt AlaRS. Consequently, the mitochondrial enzyme cannot charge cytoplasmic tRNA Ala . All insect mitochondrial AlaRSs appear to have split apart recognition of mitochondrial from cytoplasmic tRNA Ala by translocation of G:U. This split may be essential for preventing introduction of ambiguous states into the genetic code.