A minimalist glutamyl‐tRNA synthetase dedicated to aminoacylation of the tRNAAsp QUC anticodon

摘要

Escherichia coli encodes YadB, a protein displaying 34% identity with the catalytic core of glutamyl‐tRNA synthetase but lacking the anticodon‐binding domain. We show that YadB is a tRNA modifying enzyme that evidently glutamylates the queuosine residue, a modified nucleoside at the wobble position of the tRNAAsp QUC anticodon. This conclusion is supported by a variety of biochemical data and by the inability of the enzyme to glutamylate tRNAAsp isolated from an E.coli tRNA‐guanosine transglycosylase minus strain deprived of the capacity to exchange guanosine 34 with queuosine. Structural mimicry between the tRNAAsp anticodon stem and the tRNAGlu amino acid acceptor stem in prokaryotes encoding YadB proteins indicates that the function of these tRNA modifying enzymes, which we rename glutamyl‐Q tRNAAsp synthetases, is conserved among prokaryotes.