Dual Routes for Bacteriovorus bdellovibrio Asparaginyl‐tRNA Formation

Abstract

Two distinct paths have evolved in nature to attach the amino acid asparagine (Asn) to its cognate transfer RNA (tRNAAsn), an essential step in translation. In the first (the direct pathway), Asn is directly ligated to tRNAAsn by asparaginyl‐tRNA synthetase (AsnRS). In the second (the indirect pathway), a non‐discriminating aspartyl‐tRNA synthetase (ND‐AspRS) attaches Asp to tRNAAsn, and then GatCAB transamidates the Asp to Asn on the tRNA. Bioinformatic analysis predicts the predatory bacterium Bacteriovorus bdellovibrio codes for both pathways. Our work has focused on whether B. bacteriovorus encodes a ND‐AspRS and GatCAB for tRNA‐dependent Asn biosynthesis. Our studies, using the E. coli Asn auxotrophic strain JF448, demonstrate that together the B. bacteriovorus AspRS and GatCAB can synthesize Asn on tRNA. The non‐discriminating nature of the B. bacteriovorus AspRS is being further verified by using the E. coli TrpA34 system and in vitro studies. We speculate encoding dual routes for Asn‐tRNAAsn formation enables B. bacteriovorus to grow efficiently in the presence and absence of a host.