A minimalist glutamyl-tRNA synthetase dedicated to aminoacylation of the tRNAAsp QUC anticodon (original) (raw)

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 modi®ed nucleoside at the wobble position of the tRNA Asp QUC anticodon. This conclusion is supported by a variety of biochemical data and by the inability of the enzyme to glutamylate tRNA Asp isolated from an E.coli tRNA-guanosine transglycosylase minus strain deprived of the capacity to exchange guanosine 34 with queuosine. Structural mimicry between the tRNA Asp anticodon stem and the tRNA Glu amino acid acceptor stem in prokaryotes encoding YadB proteins indicates that the function of these tRNA modifying enzymes, which we rename glutamyl-Q tRNA Asp synthetases, is conserved among prokaryotes.