A dual-specific Glu-tRNA Gln and Asp-tRNA Asn amidotransferase is involved in decoding glutamine and asparagine codons in Acidithiobacillus ferrooxidans

Abstract

The gatC, gatA and gatB genes encoding the three subunits of glutamyl-tRNA Gln amidotransferase from Acidithiobacillus ferrooxidans, an acidophilic bacterium used in bioleaching of minerals, have been cloned and expressed in Escherichia coli. As in Bacillus subtilis the three gat genes are organized in an operon-like structure in A. ferrooxidans. The heterologously overexpressed enzyme converts Glu-tRNA Gln to Gln-tRNA Gln and Asp-tRNA Asn to Asn-tRNA Asn. Biochemical analysis revealed that neither glutaminyl-tRNA synthetase nor asparaginyl-tRNA synthetase is present in A. ferrooxidans, but that glutamyl-tRNA synthetase and aspartyl-tRNA synthetase enzymes are present in the organism. These data suggest that the transamidation pathway is responsible for the formation of Gln-tRNA and Asn-tRNA in A. ferrooxidans.