Co-evolution of the archaeal tRNA-dependent amidotransferase GatCAB with tRNA Asn

Abstract

The important identity elements in tRNA Gln and tRNA Asn for bacterial GatCAB and in tRNA Gln for archaeal GatDE are the D-loop and the first base pair of the acceptor stem. Here we show that Methanothermobacter thermautotrophicus GatCAB, the archaeal enzyme, is different as it discriminates Asp-tRNA Asp and Asp-tRNA Asn by use of U49, the D-loop and to a lesser extent the variable loop. Since archaea possess the tRNA Gln-specific amidotransferase GatDE, the archaeal GatCAB enzyme evolved to recognize different elements in tRNA Asn than those recognized by GatDE or by the bacterial GatCAB enzyme in their tRNA substrates.